Thanks guys. I finished up a few hours ago. I have the billet accel distributor that has the screws for adjusting mech advance. I removed the purple spring (the heavy one) leaving on the light spring. Initial timing is 18 degrees, mech seems to be all in around 2400-2500 and it is right at 38 total, so adding 20 mechanical.

Tuning idle screws have about 19-20 in steady vacuum at about 950 RPM. Using vacuum advance hooked to manifold vacuum (i.e. not port) and it is adding around 18 degrees at idle/cruise. Seems like a lot? But for cruise probably okay. Seems to help clean it up.

This is a stock (rebuilt) 383 (150 PSI cranking compression, stock cam) with an RPM intake and Holley 750 DP (currently with stock jets), headers, etc.

Really hot here today, going to take it for a test run in a few hours.

Thanks for all the help!