I'd be interested to hear how your trick turns out. I have a very similar setup (same heads etc). I gave up with the stock distributors as like you say, you need about 12 deg initial for the engine to behave well at idle and then the total somewhat less than 38 to not get a ping with premium gas. I ended up changing to an MSD distributor (they are great) with 12 deg initial, 31 deg total advance and running cooler NGK plugs, UR6's to get rid of the ping. The plugs made a big difference and I am now planning on giving it some more total advance to see what else I can get out of it.
69 Sportsroof, 351C, 4spd toploader, Restomod BOSS 429 clone - the one and only (?) 1969 BOSS 351
http://home.swbell.net/boss351/mustang/boss1.jpg
http://stangnet.cardomain.com/user/adamg69
69 Sportsroof, 351C, 4spd toploader, Restomod BOSS 429 clone - the one and only (?) 1969 BOSS 351
http://home.swbell.net/boss351/mustang/boss1.jpg
http://stangnet.cardomain.com/user/adamg69