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

Where are the rings gonna end up relative to the deck?
and will they survive there?
Recheck your math;
A friend of mine did this with used factory pistons, (don't know which ones) without spacers. It's been a strong street-runner nearly as long as mine has (since 1999)H
Yes, Top ring land is very important. I will be be shooting for bout 1/8th" - 1/4" from top.