To me . . .
Intake manifold choice is good. The plugs to block of the not-needed EGR should be in the install kit with the manifold. The noted valley pan gasket kit is good, too. The paper gaskets are needed to keep the beads on the metal gasket from putting a pattern on the softer aluminum intake's gasket surfaces. I would fill the beaded indentions on the metal gasket with black, high-heat silicon sealer and then put a skin coat of the same sealer on the paper items before installation, letting it all cure for a day or so prior to installation. This makes, from my experience, a very tight seal between the manifold and cyl heads.
I'm not sure of the allure of the Brawler carb, other than price. They do have a lot of adjustability with their removeable/changeable air fleeds in the upper throttle bore area, BUT you might get into some trouble by changing them without some knowledge of what they do and why, possibly.
If price is an issue, possibly the Summit-branded 4bbls (which are old Ford design carbs) with annular discharge primary venturis can be the "hot trick". Or an Edelbrock AVS2 with the same style of annular discharge primary venturis.
A possibly emerging issue with the Holley 4150/4160 and spreadbore 4175 carbs is that the accel pump housing is logically located on the bottom of the primary float bowl. This ensures the pump easily refills after each pump shot discharge. BUT being that it's at the bottom of the float bowl, should it ever start to seep, it can empty the float bowl onto the intake manifold. Which might cause other things than just a discoloration of the aluminum where the fuel drops fall. Holley does make ethanol-resistant pump diaphrams now.
The phenolic spacer might seem to be a good idea, but . . . it might not really be any better than the stock OEM base gasket used back then. Same thickness, but the phenolic item does not have any bushings in the stud holes to keep from uneven-torquing the hold down nuts. I learned that lesson when I cracked the baseplate on a Carter AVS 4732S on my '70 Monaco 383 4bbl back in about 1976. I was seeking to help the hot re-start issue with a popular base gasket insulator stack of alunimum plates and softer gaskets. That last little bit of snugging-down did it. OUCH! New carb time. And, no significant difference in the hot re-start issue either! From then on out, nothing but Chrysler OEM base gaskets with NO issues.
Other things? The necessary throttle linkage bracket from Holley or Edelbrock, to bolt to the existing lever on the carb. Plus some wiring and OEM-spec connectors/terminals to power the electric choke from a keyed power source. You can run the wire across the edge of the cowl with the existing harness, then have it make a lh turn with that harness, straight down the rh valve cover and to the carb. With a bit of finesse and such, it will be hidden to many eyes. You can re-use the existing carb stud for the throttle/kickdown/cruise control linkage you now have.
You MIGHT need to readjust the existing throttle cable in its mount at the rear of the intake manifold. With the new carb installed, just loosen the adjusting nut and slide the cable forward in that mounting. Hopefully there is enough adjustment for that to happen. Similarly, the kickdown rod will need to be slid forward, too. Hopefully, you can slide the front section forward to get what you need. There might be a gauge hole in the kickdown bellcrank to put a small screwdriver into so you can tell if you will need any extra "extenders" in that area?
No mention of the engine and your intended use, yet? Presuming with the 383 2bbl, it has the normal 2.76 rear axle ratio and P225/75R-15 tires? Same OEM cam? Single exhaust?
Now, for some reality issues. The primary side of any 600cfm 4bbl will be the same as the Carter or similar 2bbl that is now on the car. 1.56" throttle bores. Which means that you might not feel anything special until after about 3000rpm. How much time do you spend in those higher rpm levels? General drive-around things might feel a bit crisper in throttle response due to the added refinements in venturi booster/accelerator pump discharge nozzle designs since the later 1960s (when the carb was designed) and fuel mpg might slightly improve on the highway due to a possibly leaner calibration. But that is to be seen when it might happen.
I don't recall
@saforwardlook recommending a looser torque converter per se, BTAIM. To me, the term "looser torque converter" can mean many things. Chrysler had "low stall" and "high stall" designations for OEM torque converters, with the "high stall" designation usually on the 10.75" diameter converters (which also took 1 qt less to refill the transmision they were installed on). My '70 Monaco 383 4bbl has such a converter on it from the factory. But getting a "higher stall" converter in the aftermarket can seem to be a big crapshoot.
The "low stall" converter with (suspected) 2.76 rear gears is a good combination for highway driving. At normal highway speeds (like 55mph+) the converter is locked-up as you would expect it to be. But that tightness can also put a little damper on off-line acceleration, which is one of the compromises in torque converter design, by observation. With 3.23s, the looser converter can work well as by the time you get to 60mph, the converter on the verge of being locked-up as expected.
In these torque converters, when I mean "locked-up" I mean that there is very little slippage in them. Whereas in the later "lock-up" torque converters, a mechanical clutch in the converter applies and "locks-up" the two halves of the converter for better fuel econony. I wanted to mention that distinction.
On my '70 Monaco 383 4bbl, 3.23s w/P225/75R-15 tires, which makes 25mph/1000 engine rpm, I noticed that at 62mph, the throttle response (think one of those famous "hairs') became very "tight". One hair's more throttle was added, speed immediately increased. At 60mph and lower in 3rd, throttle response was a bit more soggy, by comparison. Yet on our '66 Newport 383 2bbl 2.76 car, throttle response was linear at all speeds. No "soggy below __ mph" or "tighter above ___ mph" situation. With the 2bbl having the 11.75" torque converter. Key thing is that by the time you get to 60mph, the converter needs to be locked-up of you can lose fuel economy, by observation. Unless you take notice of this and drive with a steadier throttle foot, from my experiences. Another story.
For reference, the 383 in my '70 Monaco has the same 256/260 cam as your 383 2bbl has. But it also has the HP exhaust manifolds and dual exhaust, from the factory.
AND . . . do not forget the very possible need for a 4bbl air cleaner base or an aftermarket air cleaner assy. Just watch the height of the new air cleaner/carb/manifold combination. You can reference the top of the air cleaner to the top edge of the cowl, as it now sits, for example. Then, for good measure, close the hood CAREFULLY, for the first time, when everything is installed. IF something seems to be resisting, STOP then and verify what it might be. Better than an extra bulge in the hood's sheet metal.
One other thing, I like to use hardened carb studs rather than the softer silver ones supplied in all of the carb install kits. A bit of lube on the lower threads can ensure they all screw in smoothly and fully. Then use a flat washer under the nuts to hold the carb securely.
Sorry for the length. Lots of little things I've noticed and experienced over the years,
CBODY67
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