engine casing

Hey everyone new to this site but I had a question on changing the stock piston an rings to a 12:5:1 piston. Here's my deal sent the head off to have new valves and port work done but also thought about changing the piston as well, here's my question since the cylinder is nikisil and has minor...

So my cousin got T-boned on my quad while cruising country roads. anyways.. I'm doing a frame swap. I tore off the front and rear end and I was looking the engine over and there is a crack on the right casing above the rear engine motor mount. I WILL NOT. split cases and replace the case.. So...