Use the 400 block, 350 rods, 5.7 inch, or 6 inch rods and a 350 crank to make torquey 377. There is less expenisive machine work involved than a 383. No block clearancing necessary. KB sells pistons to do a 6 inch rod in a 400 with a 3.48 inch stroke for $261 a set which is only $25 more than their standard 350 pistons. Aim for a static compression ratio of 10.5:1, put some AFR 190cc heads on top of a zero decked block and a Comp Xtreme Energy cam inside. Top it all off with a high rise dual plane like the Edelbrock Performer RPM and a 750-850 cfm carb and you'll be set to make some serious midrange power on pump gas.