[Rich Biebel]

305-350 cast cranks were the same casting number and the only difference was the factory balancing. If I recall correct the casting number was 448...last 3 and if you look at the depth of the holes on cranks from a 305 vs a 350 you wll see a big difference in hole depth....the 305 bobweight was lighter so the crank had deeper balance holes drilled.

You could use either crank in either engine but needed to address the balance issue......

There is no difference in the counterweight overall diameter that I can ever recall....