'70 C10 Starter Issue

[Plan Boost]

I've looked around through the forums and found many discussions on crappy starters, but their symptoms are sort of different then mine. I've replace my flexplate and put two different starters on there, both work fine for literally a day, then I go to crank it the next morning and it starts to grind. I go to inspect the starters and the housings are cracked and bolts are bent. I torque'd them down, checked clearances and everything. I'm at a loss, I even put the original starter back on it and it broke the housing as well. The motor is "high compression", but nothing that crazy...

My main concern is if I'm missing a bigger issues. I don't want to keep wasting time and throwing starters at it when something else is wrong.

The next step to me is just buying one of the high dollar high torque starters from Jeg's. My ultimate goal is to just sell this truck and I wold feel awful if I sold it with a half-butt fix and it broke on the next owner...