383 tune up advice needed

First thing needed is timing for a given rpm.

For a 100% factory setup, go with the factory.
Assuming its not 100% factory (incuding distributor) then this chart is helpful, especially if the engine is hot rodded.
Distributor starting point for a curve

This explanation from Chrysler on the purpose of timing is very helpful. See them here total timing reading accurate with no load?

If you don't have a factroy distributor, or if its a replacement my suggestion is to get some timing tape and measure the timing from as slow as the engine will run, then every 200 or 250 rpm up until it stops advancing or you don't feel safe. Then you can plot the advance curve and see what needs to be done, if anything to the advance.

You can use the pre-emmissions era 383 and 440 factory timing as a baseline.
See this thread: Total advance question
Notice the initial timing on those e ngines was 12.5* BTDC at 550 - 600 rpm. At least a couple degrees more initial was acceptable if the fuel allowed. With a cam that has more overlap, higher initial may be needed. See the first link. It also may have to idle higher, maybe 700 or 750 rpm.
Be alert to the fact that the distributor intended for a 600 rpm idle may already be advancing at 700 or 750 rpm.