Engine damage / 440 RB

"piston 0.031" over deck"
There's your problem. He probably knew that was a mistake if he enlarged the chambers and used that gasket. Have the shop take .020" off the top of the pistons and use emery to smooth the machining edges if that's not done already. The look at the camshaft, then the timing and carb's fuel curves. The problem is it's in a wagon. In something easier to move it probably would not have been a damaging issue.