383
Well, if it has a good compresion test reading, a mild cam with a 4bbl intake and carb will do very nice. As far as the heads go, just a good prep will go far.
Think. The Raod runners came with a 335 HP version. A mild cam will give a few more ponys with other add ons, you could crest 360 HP without batting an eye about drivabilty.