1994 Ford Ranger manual

Hi I'm hoping you can help I've been working on my
Ranger for about 6 months my clutch went out
when I first bought the truck so I replaced the
clutch and it seem to be doing fine but then my
starter went out ever since I change the starter it's
been making a grinding sound most people say it
could be the flywheel but I had it surfaced and the
guy said it was fine well when I put a new starter in
there it would make a loud grinding sound but it
would start the truck it would only work for about a
week before I would have to replace a starter again
I have put eight starters in this truck within the last
4 months and I have gone to every website that I
could think of to find the original starter that goes
in a 94 ford Ranger manual 4.0 but I am unable to
find anything that would work with it I was kind of
hoping you would have some ideas of what I can
try