I have a chance to get a 90 nissan fairly cheap. Problem is it has a bad piston (holed from incorrect sparkplug). Looking around I find few parts sources for nissan motors. Is this worth trying to find parts for and rebuild? Would love to replace the current 70 I have with a 90 but not if it's going to be more headache and cost to rebuild than it's worth.... Any clue (ballpark) on cost to rebuild the powerhead? Any input appreciated.