I ditched my carb spacer because I thought that it decreased vacuum signal.
If carb is heating up after a hot soak, my questions would be:
Is the carb normal the rest of the time? If not, rebuild?
How is the cooling system? Fan shroud?
Is the fuel line hot? If so, can an insulator be put around it?
My thoughts, Ben
Over the years, there have been various types of carb base gaskets/insulators which were SUPPOSED to help hot re-start issues, NOT only on Chrysler products, but also Chevrolets and such, too. Some were more heat deflectors of aluminum with soft gaskets on each side. Holley sold some like that as there were also some OEM GM items, too. The MIGHT deflect some of the heat crossover heat from the carb, but whatever heat is not deflected is caught by the air cleaner assy, I suspect.
Mr. Gasket also had some insulator stacks, alternating aluminum pieces and soft base gaskets for a build height of about 3/8" or so, or basically the thickness of the normal OEM insulator base gasket. EASY to crack a carb base, even if you are careful . . . which I found out myself on my '70 DH432N AVS. Looks good, but "not good".
There used to be some wood insulators that the racers used.
My best experiences have been with the OEM-style thick paper gaskets with plastic or metal bushings in the carb stud holes (to prevent uneven torque on the nuts). Available in Holley, Edelbrock, or possibly other brands. Open center, divided center (as is OEM on my '70 383 "N" Monaco), or 4-hole versions.
Chrysler B/RB engines do seem to have worse hot soak re-start issues than other brands, for some reason. No real fixes, other than to install an aluminum intake and configure the insulator pad that goes under the intake to allow for air flow under the heat crossover area of the intake and also keep the breast plate gasket from having harmonics in it. Blocking exhaust heat from the gasket, with special intake manifold gaskets, might be in that mix, too. On 2bbl intakes, the under-manifold insulator and blocking exhasut heat from the intake might be some of the better options.
THEN make sure the fan clutch is working as it should upon re-start. You should hear it before it kicks-out, for example, unless the temps through the radiator are too cool for such.
The radiator? Use an IR heat gun to check for even heat, top to bottom. The fan clutch will not kick-in unless it sees heat coming through the radiator. Hence, a clogged radiator is cool in that center area and the fan clutch sees only ambient heat, not engine coolant heat, so it does not work as it should under hotter engine temp situations.
AND also might ensure the ignition system and spark plugs are in good condition, too. Making sure that it produces enough spark to get things fired-off quickly. In any weather. With your existing spark plugs, take a pair of pliers and gently twist the ground electrode so that about 1/2 of the center electrode is exposed, rather than being covered by the ground electrode. An easy way to get the spark more exposed to the air/fuel mixture at the recommended gap. Otherwise, you can also file the ground electrode back so that it only covers 1/2 of the center electrode (as the old Champion J-gap plugs were built). The NGK V-Power plugs work well, but the NGK fine-wire Iridiums make a bigger POW with each spark (YouTube videos on that situation).
Past these things, use 1/3 accel pedal input when starting, per Chrysler recommendations in the owners manual.
MANY more things to consider than we had in the mid-'60s when the cars were newer, by observations.
Phenolic spacers worked for me. 1/4" thick. About 15 deg cooler carb temp (with a IR heat gun) than before. I would have gone to 1/2" but it didnt fit under the hood. But I have the unusual luxury of a big air cleaner that holds the heat around the intake. Like the other guys are saying there are probably other reasons you and I are having heat issues that should be solved but until it gets ironed out you can certainly try a spacer. If you cant find a premade one you can make one out of a small sheet. That's what I ended up doing for 1 of the carbs. You can paint it if you dont like the brown edges. And you likely will need longer mounting studs.