I'm expecting the new gauges and pan filter today, so I didn't start it to get initial timing. I ended up removing the existing gauges and will wait until this weekend to really dig into this. It's supposed to rain today and I'm out in the elements, so I'm not going to go too deep. But I did pull the distributor cap to verify the mechanical advance as best I could. The springs are blue, which according to MSD's instructions are 2nd lightest. I tried to look at the bushing stop, but it's pretty hard to tell whether it's blue or black. In either case, the advance looks to be all in around 3k RPMS and is a total of around 20 deg
If you've ever messed with the stop bushing in one of these distributors you'll know how much of a PITA it is. In this pic, it's under the innermost pin that the spring on the right is attached to. So, to confirm exactly what I have, I remove the nut from underneath to be able to remove the bushing. Once I get it out I'm able to confirm, without a doubt, that it's blue.
Now I know what the ignition curve is. 21 degrees total advance at around 3kRPMs. Way back when, when I installed all of this, I played with the different springs and bushings and found that this setup worked the best. I saved the others, but as with the Holley book, they've disappeared somewhere. Only with this I'll make a more educated guess and say that it was lost or misplaced in a move at some point. So if I think I need another I'll have to order one.