M T f U! I'll do it myself.

What did the bearings look like?

So, let me get this rite, #2 piston lost a top edge long ago. Not a problem, It's a Detroit.
All else looks good.
Explain to me again Lucy, ,,, why are you tearing down a good running Detroit??

I luv ya kid. Just got to throw stuff at ya.
But really, I don't see any emergency issues,,,, yet.

You just wanted to get into one??

How bad did the starter look as you were cleaning it up?
What did you see to change your mind?

As long as your looking at a starter, How does that ring gear look?
What the starter grinds on to rotate the flywheel?

That starter has the rotating head also. Ensure the new starter has its nose aligned in the same position before mounting.
Invest in a new starter also (not rebuilt).

Ole Bert 32V starters have not been touched since we have owned her. Could be original.
Not pretty, but never failed.
One day, converting to 24V MT50s. These will be new then. a few bux extra but I'm not going to touch them again for at least another 20 years.

Naw, Not worn, Well broke in.
Think; Less Friction.
Real high performance engines.

You have to remove the engine or tear it down to get the starter out? Sounds like it is a PITA under any circumstances. I think I would buy a new starter from a reputable manufacturer AND have it bench tested before installing. It would royally suck to do all the work you’re doing then have a starter issue.

Cleanslate I respect you for taking this on. You will learn a ton.

I had access to one of those tools. Must have been older than myself (that's old). On some of the real old installs, pending the clutch, fly-wheel & bell-housing, there was just a plate opposite from the starter. You could mount the starter on either side.
Now days to use this tool, you have to remove the starter.
Not worth it if access to the front bolt is available.
I was just chatting on another thread about a similar tool on MAN engines. You don't need to remove the starter for that one. Port in the fly wheel ready to use in a minute.
Either tool; it's slow turning the engine with a hand ratchet. Air ratchet would be a great help.
You got compressed air on board?

Usually, you can not reach that bolt with a wrench, only a socket with extension.
A better 12 point socket/bolt can center, insert and apply more torque than a regular bolt head.
Good ideas when working in the dark or out of sight on an old rusty bolt.

Just another thought, from some long ago geezer, that tried to make servicing these engines easier.
Not many of these folk left (if any).