The 258 crank is a drop in. When making the stroker 4.0 [using the 258 crank in the 4.0 block] you use also the 258 rods. Install the 4.0 pistons on the 258 rods and crank and you now have 276.5 cubic inches. You can use most any 258 donor crank that is found but most use the 72' through about 77'. Reason being they are the 12 counter weight version that are much heavier and durable. Truth is, if you don't plan on revin' the poop out of the thing any 258 [3.895 stroke] crank will do.
