IIRC there is a # stamped on the arm of vac can IIRc you get about half that # in mech advance. so you can search out a can that will give the advance needed.

my understanding is with a stock dist on ported vac it adds to much mech advance. up to 50* or more.

the can is adding mech advance and the weights are adding more mech advance when rpm increases.

I tried last night to swap it onto ported and the results were poor.

I removed can from full vac, rpm drops, adjust back up to 750 curb idle, hook line to ported vac, adds no mech advance, test drive and 1/2 throttle from stop it pings and spark knock.

change back to full vac on can and adjust curb idle back down to 750, test drive, no ping or spark knock.

dist & carb working together may be what I stumbled upon on mine.

on my junk, following the steps in Don's book and not the way I have always done it fixed a lot of things I have put up with for yrs.

I will be hooking up the vac gauge on ported vac to see what it is doing at 1/2 throttle from a stop. and get a WOT reading.