351 Windsor Ignition Timing

Need some guidance. I have a 69 Mach 1 with a 351W and I'm trying to dial in the ignition timing and fuel mixture. The motor is built up pretty strong with a solid cam and lifters, file fit 11:1 compression pistons, bored .030 over, balanced and a 3 angle valve job. It also has an Edelbrock Performer intake and a 750 cfm Holley with vac. secondaries. This engine really likes octane and timing. I have to run a mixture of 110 octane race gas and premium pump fuel, the intital timing is set at 6 degrees and when I hook the vac advance line back up it goes up to about 26. When I rev it up it appears to go as high as 55 but it runs awesome, great power and throttle response. I thought anything over mid 40's BTDC is dangerous but I was wondering with the set up and fuel I have am I OK? I have also been told while on the dyno is is running rich. Carb has a fresh rebuild and was jetted down a few sizes. Would the race gas effect the dyno fuel air reading? The mixture screws on the carb are only open about a quarter to a half turn, is that normal? Like I said it runs awesome but I just want to be sure I'm not going to damage anything.

Thanks,
Jim

I just have the stock dizzy but I replaced the points with a pertronix set up. I have 26 degrees mechanical and I have tried it with no vac adv set at 12 initial for a total of 38 but it seems to run a lot better with the adv hooked up. How am I getting more total adv with the vac adv hooked up? I thought total adv was inital plus mechanical? With vac avd hooked up I set timing at 6 inital, getting 26 on vac adv and I'm getting over 50 total.