I've looked at a lot of posts and videos without getting much help in trying to get this done.
Many years ago, I replaced my starter.
Not all that many problems.
I got it done with one from a wrecking yard.

Now, the starter has died again.
At first I thought it was a bad cable.
Turns out it's most likely the solenoid.
Can't confirm or fix that until I get it removed.
Plus, it seems that one cannot buy just a solenoid,now.
It's either a new or rebuilt starter to get it done.

The upper bolt is giving me problems, can't get it to loosen up.
A ratchet, isn't long enough, can't get enough cheater bar on it.
a breaker bar has too much slop in movement, a cheater bar doesn't help.
An impact wrench [supposedly 500ft-lbs], even with the air pressure turned high, won't budge it.
I've tried from the top, bottom and side.
Gone back every day for over a week and tried something new.
Getting no where.
I just sprayed a WD40 lookalike on the bolts for the headpipe to the manifold, getting ready to drop the headpipe to get more room.

I'm beginning to get desperate.
Thinking about cutting, grinding and/or drilling on the bolt to remove the head - breaking, grinding, and/or cutting the starter's flange off.
It'll probably be $hi4t canned anyway.
I'm getting desperate, but won't pull the engine to get it done, ... I don't think.
Might be able to get it and a lot of other things loose with some dynamite.
Any suggestions? ... Other than dynamite.

 

C4. If yer gonna do it, do it right.

WD-40 doesn't really help. PB Blaster, or something similar is FAR more effective. Then the impact. Make sure you are turning it the right way as well. Worst case, heat it up, then hit it with the impact. Should come off.

 

What I called a WD40 look alike was PB Blaster.
I'm naturally LHed, so have always had trouble keeping L&R straight, even N,S,E & W, too.
If I don't stop and think, I am likely to mix them up.
If I did turn it wrong, it was only the 1st time with a ratchet box end.
I stopped, checked, and made sure every time before trying to loosen it.
I was paranoid that I might be making it worse.

I hadn't applied heat.
I think I have some propane. If not I"ll pick some up and give it a try tomorrow.
The impact wrench is a small Husky.
Not top of the line but still rated as 500 ft-lbs @ 90psi.
It may be exaggerated a bit, but it was solid when I turned the pressure higher.

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EDIT:
I found the propane bottle and nozzle - Got heat for tomorrow.
After thinking about it, I'll heat the bell housing to expand it away from the bolt.
I'll even try icing the bolt's head to cool and contract it.
Hopefully I'll be able to break it loose with the impact wrench.
Note:
My understanding is that it is a 5/8" bolt.
I have been using a 16mm socket and wrench on it.
5/8" is loose, adding much slop to trying to get it out.
16mm is much snugger with little slop but not to tight, much more secure fit.
Didn't help much but made me feel better.

 

yes it is a 5/8 bolt, 7/16 threads. The top hole of the starter is 14mm and takes a bushing - if the bushing was left out and you just have a washer on it, the washer may have caved in and is acting as a lock for the bolt.

 

All ready to go on this, but its raining.
Should dry up this afternoon.

When the starter was installed, I used the original bolt, don't remember anything about a bushing.
Can't look right now, car's on the lawn and the plywood I've been laying on is all wet. but memory tell me that I had seen a washer under the head, not sure if it was flat or split.

I'm in my upper 70s and been a shade tree mechanic all my life, since I was 15 doing everything from changing tires to pulling and rebuilding engines.
These are normal conditions for me, and why I hate working on a car, but too cheap to hire someone else to do it.

EDIT:
Not sure if I'm thinking of something else, but there may have had a bushing in the bell housing that protruded out to hang the starter on when installing it.

 

are you on the starter bolt or the trans bellhousing bolt right next to it? made that mistake before

 

The bolt I've been fighting goes through the starter's flange, then into the bell housing.

Haven't got back on it yet.
Can't find my 1/2 to 3/8 reducer to make the impact fit the extensions.
I remember doing something with it so's I wouldn't loose it.
Now I can't find it, story of my life.
I ordered a pair of them from Amazon, should be here by Friday.
I'll continue looking, though I have torn the place apart a few times looking for it already.
I'll probably find it just before the new ones arrive.

 

yeah I know the top starter bolt goes thru the starter and into the bellhousing. Duh. But there's a bolt that goes thru teh engine block, also into the bellhousing real close to that bolt. and reaching up there blind its easy to mistakenly put the wrench there instead of on the starter.

 

Don't know which bolt your referring to, nor ever been misled by it.
Don't need to know now.

The adapters arrived yesterday.
Today, heated the bell housing and jacked the impact's air up to 120#.
It came out so quick and easy I had to crawl out from under to go look to see.
The split washer under the bolt head had scrapped the surface of the bell housing deeply.
The hardest part was fishing the starter down and out to the ground.

I have ordered a new starter from Amazon.
Estimated to arrive in 5 days.

Since the epidemic has gotten old, the holidays are over, and Amazon has begun flying their own planes to Hawaii, their service has gotten better even though they won't ship a lot of things they used to.
I was surprised the starter will be sent.
Thought I'd have to get a rebuilt locally.

 

Well now that you have it out look up there on the engine flange next to the hole where the starter was and you'll see it not far from the edge there. When reaching around the starter somewhat blindly it's easy to get on that one instead of the one you meant to