from what i can tell the deck on a 305 severly limits what can go in.so...my question is this.what is the largest crank that can fit in a 305?

 

A 3.75" stroke crank from 400's is a swap that many have done. It comes out to about a 335 (not sure on overbore/displacement #'s). But then again, it's a large waste of energy on the 305. Do the smart thing and find a 350 core to build (with the 400 crank to make a 383), and get that ready while you beat the bejesus out of the 305 until it blows up.

 

bored and stroked 305=337
bored and stroked 350=383