340

You mean because of the difficulty of finding a good used one.
Some guys have bored 318s out to 340 size
You can bore a 360 out to 340 size.
If you really want a 340 put up a want-ad. If you can't find one Pm me; I have several you can chose from.

Pm me what you have... I just bought a new 4 inch crank last week and it needs a home