Starter Blues

My stepson has an 82 Ford F100 with a 302, not the original motor. Best I can find the motor is a 79 model. We have put 5 starters on this thing because they keep tearing up. We have changed the relay, the ignition switch, flywheel, tried it with & without shims with the same results. When first installed, the starter works perfect, but after just one day it starts making a grinding noise & not wanting to turn the motor over. The teeth on the ring gear and the starter are both fine, no chips or cracks. This is driving me nuts! Any help appreciated!!

Oh it’s also a manual, 3 speed.

Fords of this era had two types of starters. Long nose and short nose. This refers to the section of the starter where the drive gear gets forced into the flywheel. Are you sure you’re installing the right nosed starter?

Tester

As right as I can be…even the bell housing doesn’t look deep enough for a long nosed starter. The parts store supposedly matched the starter with the flywheel.