Most of my experience has been with our big blocks and Hemis. I have messed with a some small blocks, but have much more time with the BBs and Hemis which really respond to ignition advance so this is directed primarily at the BBs and Hemis.

I don't really understand the place that manifold vacuum has in this. Our big blocks/Hemis like a lot of lead at idle and the bigger the cam the more lead they like. They also like the advance in as soon as can be, but kept out of detonation. That is the part where for me, the manifold source fails. It drops advance at a time that my experience shows that the engine wants it.

On my street combos, I typically run 25+* of initial. As much as I can and it still not hit the starter on hot days. And then all in by 2,000. On the wedges the total is usually 32* to 34*. On my current Hemi, it likes 31* for what ever reason. As I said before, I use a hand held vacuum pump to experiment with how much it likes at cruise. The change in exhaust note is very noticeable as you change the amount of advance and is a good starting point to set the amount of advance for cruise.

I use a stock Mopar distributor and JB Weld the slots to get the amount of advance that it likes. I also use JB Weld to add weight to the advance weights along with micro springs from a hardware store to get the rate right. It takes some trial and error and multiple disassemblies of the distributor, but after a time or two, it goes pretty quick.

For me, the toughest part is getting the vacuum can stop at the right place. The opening point is easy of course, since Mopar made that adjustable. There used to be a wide selection of vacuum cans with different amounts of vacuum advance. But that is not true anymore, so modifying what we have or can get is the way to go.

So my preferred mix is modifying the weights and springs in the distributor to get the initial timing and the mechanical advance where the engine is happy and then using ported vacuum for a modified vacuum advance. That's the way Mopar did it and the way that has worked very well for me forever.