why would you take out 402 big block ?? the stock heads will out flow the small blocks even if you spend big $$ the stock big heads with not much work they will kill your small$$ headswith stock parts in them bore the 402 to 0.30 and try to get it to 9.1/5 or 10.get edelbrock rpm or air gap. do not cut heads out for big valves with the small bore it is a waist of money do a bowl job and a good 3 angel valve job and ss valves for the cam at 0.50 230 230 544 544 on 110 or a501 527 214 224on 110the bottm end on big blocks are ROCK solid you do not need to spend much here put mich 77 bearings in it run oil clearances at .002.5 rods & mains a good set of rod bolts arp a good oil pan with a tray and some good machine work this 402 will kick a mud hole in that 383 and will last longer