With a different distributor, using factory settings for your car will not work. Where is the timing set now?
In order to see what you really have, in the way of the distributor curve, is to get a "dial-back" timing light. With the engine at hot base idle, see where the timing is set, then turn the dial to "0", to double-check the accuracy of the timing mark on the balancer.
With the vac advance unhooked (it should be hooked to a ported vacuum port on the front of the carb, very little vacuum at base idle, rather than full m manifold vacuum at the other similar port). Plug the port on the carb. Then take the engine up to about 2000-2500rpm (using a dwell tach). See where the timing mark now is, then turn the dial back to "0" and see what the reading is on the timing light. That will give you the mechanical advance that's in the distributor. Then add the amount that you initially turned-back the knob to that figure and you'll have the total advance at that particular rpm, BTDC.
In general, with the vacuum advance hooked up, when driving at 60mph and throttling-into the engine (as if to execute a mild acceleration to, say 75mph without any part-throttle kickdown to 2nd), if you hear no "trace rattle" with the gas you're using, depending upon how much initial timing is currently in the deal, you might try adding 2 degrees BTDC of initial timing to the current setting. Re-test for "trace rattle" (which is not a full "clatter"/detination" per se, just the beginnings of such). IF you add more throttle, up to WOT and it goes away, that's fine, but still might back it down 2 degrees BTDC so all is quiet, for good measure.
In the pre-emissions days of about 1966, Chrysler's B/RB total timing (base initial plus distributor centrifugal) was usually in the 36-38 degree BTDC range for the 383 2bbls (which were 9.2CR). What that meant was the initial base timing was 12.5 degrees BTDC, with the rest in the distributor. NOT counting the possible vac advance amount, just the base plus centrifugal.
So, depending upon how much advance is in the distributor, you can probably make 12 degrees BTDC as your base timing amount, if needed. For a baseline from which to start your on-road testing.
IF the distributor is a factory-style electronic distributor, there Is no real "dwell" reading that works. There will usually be one that the dwell-tach will measure, but it's determined by the control box and is not adjustable. So presume all is fine, in that respect.
With the 2.71 (std) rear axle ratio and the normal tire size, Interstate cruising will typically be in the 2000-3000rpm range. Which is on the "front side" or just past the rated torque curve of the motor. So keeping out of "trace rattle" is good, especially if there is no WOT clatter! So advancing things right up to the ragged edge of trace rattle, then backing it down 2 degrees BTDC will usually work well, vac advance hooked up and working.
With the altered equipment, it's going to be a "try and see" situation. Be sure to use the lowest octane of fuel that you plan to use in the car, too! No need to put higher octane in it, set it to operate with that fuel, IF it's not cost effective and does not result in significantly better power/economy.
Enjoy! Keep us posted,
CBODY67
