What starter can I use? 350 Chevy unknown year (69-72)

I have an old jaguar that was given to me long ago by a family friend that has
since passed on. The car received a 350 conversion but the starter was
never right. I was told that the engine was from a 1972 Chevy impala and is
a 5.7L v8. I had the transmission rebuilt and the mechanic told me the
transmission was a turbine 350 that probably came out of a 1969 Impala. So
i have either a motor from one year and a transmission from another of
someone told me the wrong thing, and im not really a car guy. The starter
has never really worked, i buy new starters that match the one that was on
the car but they dont last more than 10 or 15 starts before they begin to grind
or seize up or brake. I really don't know what starter to put in it. The ones i
have are not a problem of adding shims either, shims make the problem
worse, kind of like if i could remove a bunch of the starter metal it would work
better. Any ideas would really help, i really want to know if there are
differences in the 69-72 starters for a chevy 350. Thanks!!!