First up is just a clean and new bearings for both, and one needs a keyway cut into it, then...
I was going to try the 3/4 on a 2x48 belt grinder (48 because of size), if that seems to be powerful enough I was thinking of building a 4x36 grinder with the 2
If the 3/4 seems underpowered on the 2x grinder I'll toss the 2hp on it and just squirrel Away the 3/4 for another day
They are both open motors, I think I will just put a piece of filter cloth over the inlet and maybe some kind of guard in front to keep the majority of dust out...if I kill them no big loss, I'll just keep an eye open for a cheap TEFC