I hope this hasn't veered too far off the origional post, but... I think traction will be your only problem running mid 13's or likely much better. I put a bone stock, 60,000 mile 1965 383 (2 bbl), in a 1972 Valiant 4 door. I added a cast iron 4 bbl intake, and a 600 cfm. carb, 2" exhaust off the tiny log style manifolds. Car was complete in every way, stock interior, steel wheels, a used 727 (120,000 miles), with a gigantic stock converter, and an 8-3/4 with 2.76 freeway gears. It ran 14's the first trip to the track with no tuning whatsoever, and turned 94 Mph. in the 1/4 using only 1st and 2nd gear. Your car will be MUCH faster.