Heres what i did with a 360 awhile back, it was the best SB i owned, super screamer, ran 13.2s in a fully dressed 73 Swinger, that was on the limiter in every gear at 3700ft. Alt. I'm sure you want to keep the 3.91s, but 4.56s ran great in mine.
71 360: .060"
stock rods, ARP bolts, polished crank, everything balanced.
KB190s (.040" quench dome) Final compression was 10.3.1 with .039" FPs
Stock prepped J heads with stock valves.
XE 284H: 507/510 lift., 240/246 dur. @ 50
Hooker comp. headers, RPM air-gap, 750dp.
MP dist., MSD 6AL, timing was 20* int., 36* total, all in by 2200 rpm.
2800 11" (needed more converter, but haveing the 4.56s helped alot)
904 trans, Cheetah RM VB.
8.3/4, 4.56
PS,PB car.
Ran great on pump premium.
The car had all steel, all glass, full int. (with bench seat), full bumpers, you name it, it was there. With me it weighed around 3500 lbs., car had easy 12.9s dialed in @ that Alt. That car was a blaaaaaast to drive!!