I have ford tractor gas engine that needs rebuilt.  No one offers a gas piston for this engine, but they offer the correct dimension piston for the diesel engine.  Will this work?

I don't think this will work because a diesel piston is heavier and designed for compression ignition. The ring package is much different and the top of the piston is meant to swirl the diesel charge to its most compressed state. Simple answer is I wouldn't do it. Maybe someone else has another idea though. I'm sure you can find a gas piston that would be much closer to what you need.