Undercutting the 360 crank this much is no big deal.Guys do it to stock cranks all the time. Usually its forged,but the 360 crank is plenty beefy. It also should shed more weight in the rebalancing process.So what you will have is a big small block with a fairly light weight rotating mass,therefore quick revving.It will like to breath due to the big bore of the 340,so it's gonna luv serious heads!