[120mm]

Right now, the two most common stroker "kits" are 4.125 or 4.250 cranks, which result with approximately 431 or 445 c.i. displacement.

Knowing that, why would someone choose 431 over 445?

I'm new to stroked engines, so am curious as to what makes the smaller more attractive.

Also, what modifications need to be done to the block? Do the stroker kits just "drop in?"

(I know they don't technically "drop in"; I've built a few SBFs before, but you get my drift.)