well i have built some cast steel cranks 4 1/4 cranks with the speed pro hiper pistons i would go that way496 .but you can use the 366 crank and use 427 pistons if you need a one pc main seal 454 crank i have one fresh truned ready to go that would sell for a good price is the 366 a two pc seal you need to run a seal adapter and a internal damper the truck will not work so hot with car or light truck power water etc brackets