Use a table ban saw to hack off the 340 piston crown .

I've always wondered if you took the doors off a jeep and then drove down the road hanging out the door opening with pencil in hand, how long of a line could you draw with said pencil before the graphite ran out.

A similar method could be used to remove the excess material from the 340 pistons without the risks of cutting round material in a band saw. That's generally a bad idea.