One item of interest- - - -the heads for a 305 engine are exactly the same CC, and compression ratio as the 283 heads. No, they don't have the offset bolt holes, but they can be upgraded to larger valves without destroying a set of original 283 Power-Pack heads. 1.94" intake valves from a 350, and 1.6" aftermarket exhausts fit pretty well without a great deal of work, and the 305 heads will have the stellite exhaust seats on some models. I use these on claimer engines for some of the roundtrack racers who use my engines. They bring a 350 up to about 11:1 compression with flattop pistons, and they'll run 6,200 RPM with a 350 CFM 2-barrel in the claimer class. Your 283 will wind a LOT tighter with the right cam and a small 4-barrel.
Jerry
