I built a simialer 305 to what Tech suggested & believe it to be 300+ HP. KB143 pistons. block decked to "0" I used a Comp Cams XE256, Corvette L-98 aluminum heads, Performer Intake, 570 CFM Holley, 1 5/8" headers, 2.5" dual exhuast dual high flow cats & dynomax turbo mufflers, Pertronics HEI dist.
I had it in an 86 GMC Caballero with 3.08 posi, ran 13.70s & very consistant. didnt 60 ft the greatest, wasnt a real tire smoker eaither...3.42s woulda helped.