Ive got a spare RST engine sitting in my garage. I was thinking about building a decent spec'd engine from it. If i bought Mahle Low Comp pistons and steel rods, etc, would they fit straight on? Or would the block need machined? I dont really know much about the mechanics of it but I removed the head, flywheel and crank to have a nosey and learn myself a bit about an engine using my trusty old Haynes manual. And what would be the best thing to do with the head? Exchange it for a stage 3 or similar? Obviously im in no rush as its a spare engine! What would you all do with it?