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

Clearly I need to read this whole post, your thinking 3.79 or 4" stroke? What rod? The Hoover engine is based on a 3.58 stroke which has the bottom of the piston needing to be cut for clearance... A 3.79 stroke will pull the piston .105 deeper in the hole, that means the skirt needs to be shorter to clear the crankshaft.. A 4" crank needs the piston to be .210 shorter... Your gonna need the right pistons, not worth the risk, especially if your not already intimately familiar with all the possible problems...

Trust me, I get the redneck approach... It fits me just fine but I also know doing what you have in mind "On the cheap" still won't be cheap, but it's got the potential to be an expensive fail...