If you can get a piston with a slightly larger bore, no more than a millimeter higher on the compression hight, and the same sized or slightly larger wrist ping, yeah, you "could" use them. Just bore the engine to fit the piston, then drill the small end of the rods to fit the pins. If the piston is slightly taller, it shouldn't matter as most engines come from the factory with the piston far from zero decked. If the skirts extend too far into the block and have interference issues with the crank, grind em off. I think you're biggest problem is going to be finding a piston that matches the combustion chamber of the MG. Oh yeah, expect to spend some time and money getting the rotating assembly balanced. It's probably going to be nowhere near the factory spec balance so heavy metals will have to be used or lots of drilling will have to be done.