With your 283 short block being stock . Cast flat top pistons and stock rod bolts . I think the best heads for your build will be . The World S/R 305 Torquers . They have 58cc Chambers with 170cc intake runners . And run the 1.94in/1.50ex valves With screw in studs in-stalled . Some guy run the GM 305 heads #416 or #601 . But the GM heads more times then not are cracked . And if you find a good set they will need lot's of porting and screw in studs installed . They are 55cc to 58cc Chambers with stock 1.84in/1.50ex valves . As for a cam shaft to run . With that stock short block and your flat top C/R at around 9.25.1 . I would stay clear of the co$tly roller camshaft idea . I would run the Comp Cams XE262H Cam . This cam is a flat tappet hyd with 218/224 dur at .050 with 462/469 lift and has a 110 L/S . With your Performer intake and a 670 Holley Avenger carb and a good HEI . This 283 will run on Pump Gas and make a real 325 HP . And I am sure it will have a lot more low end Torque then with that big roller Cam . COOL