Flywheel/starter problems?

I had been having infrequent problems w/ my starter grinding that became more frequent till it wouldn't stop doing it. I replaced the starter last week and it has done it again a few times.

I initially figured I had a few bad teeth on my flywheel that were not meshing w/ the starter and also figured that w/ time it had damaged the starter spur wheel.

Since it's doing it again (only occasionally) does the flywheel teeth diagnosis sound possible or could it be a voltage issue?

Thanks again for the help.

Oh, by the way, does anybody know if either Explorers or Expeditions came w/ a 50" alum driveshaft? I've been told that one of them did and could be swaped into a classic T-5 combo.

The bellhousing was on the car when I bought it but it says NHRA on it and I was told it was a Lakewood housing. I also have no idea on the block plate but I would guess it's older than '82. Wouldn't the mounting bolts determine the alignment of the starter? In terms of the starter, I'm not sure where the one I replaced was purchased and what manufacturer but the one I just installed I got at Advance. I honestly can't remember who makes it though.

I'm hoping to swap in my T-5 this fall and will be using a late model housing and at the same time I'll check/replace my flywheel. Hopefully, the starter will last till then.