I currently have a 13.1 496 combo that is internal balanced with mallory metal added to the Eagle crank. I am using SRP 13.1 pistons and would like to swap to a 10.5 to 1 pistons to use pump gas, I am detuning my bracket motor. Is this possible without a rebalance job? :confused: Any advice appreciated

As long as the piston and pin weigh the same then you are fine. Not much chance of that, with different dome size and probable different alloys.

Thomas