Just like a stock 383HP. Can you say 425 LB Ft? Even so, I still recommend warming up the 318 first. It will keep the car running and the chance for losing interest much, much lower. Then I would work on my 400 and basically build it in the same way I would a 383HP, compression and all. That would probably reach out and touch 500 LB FT.
solid idea on warming up a smallblock for the quick and easy enjoyment with a back burner build for future shenanigans. the best part about that is you can slowly amass the parts needed for the swap scooping up deals along the way.
i'm with you on a BB build. give it some compression, work the heads a little, go with a more conservative cam, top it with a dual plane and modest 4bbl. no snarly, tooth and nails beast. no drama. everything is done by 5500 and a boat load of torque that will roast the meats on command.
