I ran 340 pistons in a 360 block in the seventies and just followed the article for Hoovers Mover in the magazine article. The owner of that car was Tom Hoover, an old retired ex engineer at Chrysler and explained how to do that for a high compression 360. You had to machine the pin bosses underneath as they would hit on the crankshaft throws and needed about 100 thou of the tops of the pistons to achieve zero deck. I ran my car with an engine like that and ran mid thiteens with a std 360 camshaft. Tom Hoovers car ran high elevens at the time.