How did you see a hole in the piston with the head still on? if you have the tall side covers, you will need to pull them off anyway. Because you ruin the gasket when you pull the head. You could almost take the head off without pulling the rocker arms, except (assuming you have an engine with the 15 bolt head, I don't know about the 18 bolt heads) except there is one bolt directly under the oil distributor, you might be able to get it out without taking the rockers off, I do know I couldn't get a socket on it to retorque the head with the rockers in place. Here again I don't know for sure which engine you have, but a 53 should have the engine that when you pull the head the pushrods will just fall over, as the holes they pass through are in the head. You won't get out of this situation easily I'm pretty sure, but unless there was some strange circumstance as to why there is a hole in ONE piston, this looks like a real good opportunity to do a thorough inspection of your engine, bearing clearances, measure the bore things like that.
