I had a 67 R/T full weight car with a late 72 engine, factory hi stall converter, felt like 3.23 or 3.55 gears, headers, factory intake, holley 750 V/S It ran 14.3 at 94 mph on slicks and would incinerate the small street tyres from a standstill. My friend bought it from me, then fitted a .509, ported RPM's milled .050, a performer intake and a 2500 stall converter.
He only ran it once best 13.0 at 105 mph. I told him it would be a dog with the .509 and to advance it 4 degrees. I think with more comp, it would have gone low 12's to high 11's. I believe the late 72 engine had the same comp as the 73 which i dont think was even 8.1.
Mick