I found the starter grinding problem the mounting hole in the block is cracked! Not good as it’s a 69 512 block.

Damn -- not good! It can be fixed but the process is extensive. Back in the day one method was a lot of preheat and a good welder using high nickle rod ... Good Luck!

If your car has the cast iron starter end housing you can always find the end housing that has the 3 bolt style, and use all 3 to retain the starter, apparently Some early BB “may” be drilled for all three, you will have to check, you could always put a stud in the cracked hole too?

I used the 3 bolt end housing before on a mid year Corvette that had that issue, it’s still good after about 5 years.

Yea that’s the plan however for now I’m gonnna use a high torque mini starter that also uses three bolts with the stud. I am on the hunt for a starter or nose of one with the three holes if anyone has any knowledge of what year and what model had this nose.

I think 66-72 Corvette/Chevrolet used them, maybe truck applications too. Any starter rebuild shop should have access to it.
The third bolt is a non knurled type bolt as most blocks are not counterbored on third inner hole.

Also make sure you use the front starter to block brace, that’s very important.

So my block is counter bored for the knurled bolt on the third bolt should I use a knurled bolt or no?

You won't find a GM housing that will bolt up with 3 bolts. You can find a aftermarket starter that will. The cast iron housing with three bolts does not line up with the block.

This is the housing that will not bolt up to a big or small block using three bolts.

Well that’s weird, I did it on a friends 67 Corvette about 5 yrs ago and it worked fine, maybe it was a aftermarket part or block had been previously drilled & tapped, I don’t know.
I have another starter with that end housing, next time I go to shop I’m going to mock it up on a block and check it . I have 33 blocks at shop so it shouldn’t be a issue, Ha Ha.

On Rays Chevy Restoration site they say some early big blocks were drilled with this pattern.