By single point, I assume your talking about a drive gear that they sit on opposite sides of?
I pulled them both for an over haul. At least Alternator and vacuum pump are very low time (50 hours or so).
Also does anyone know for sure, when switching to the L on the mag test with a key switch, is that grounding the left or right mag?
HiTech
Right is correct! When both is on, neither is grounded, but when you move to L or R, which ever is not engaged by the switch is grounded. I would also recommend that when checking mags, go from both to left, then back to both, then to right. If you go from both to left, then to right and then back to both, you will get an incorrect reading on the right mag because of uneven fuel burn when one is off and one is on. If you go back to both, from left, before going to right, both setting will eliminate the excess fuel vapor, prior to testing right mag.