You have mismatch of parts but it can work 3.91s I have run 4.56's Forget the crap about the rev's it will go or blow.Timing get it as high as you can total near to 38-40 degree's as possible I think your comp is lower then you think if not and it talks, back it off. Under the carb run a 4 hole spacer Jet wise use 70s in the frt and no more then 76-77 in rear with a heavy yellow or purple spring to start DO NOT over jet.A 650 dbl pumper would work great. Air gap is good manifold but too much for combo you have you can crutch it or go to good dual plane