1995 Blazer Starter is killing me!

Alright, it's been a while.
This starter issue is driving me crazy.
I've installed a new battery, new 1awg cables including grounds.
I've tried shims, no shims, two different starters.
One is a brand new Remy gold, heavy duty starter and the latest is a reman from Autozone.
Same issue with both.
And this is totally random but sometimes the pinion just doesn't extend far enough to drive the starter.
If I turn the key a bunch of times when this happens it will eventually engage properly and it starts right up. But I just can't figure out where to go.
I believe it's an alignment problem but I verified the proper starter and flywheel.
Sometimes it fires right up, sometimes I'll have to give it a few tries and other times I'll have to cycle the key 10 or 12 times.
Also, out of curiosity I've tried a few times when i get the first click and no crank I moved the engine a little and it will engage right away.

Any ideas are much appreciated.

Quick update just in case anyone is paying attention.
I sanded the block where the starter mounts just to be sure.
The mounting bolts are clean and so were the contact points, but I cleaned up the whole area.
No difference.

First try, click.
Second, I engages and turns over as it should.
It does this 3 or 4 times in a row, then won't engage for another 8 or 10 tries.
Then good 2 or 3 in a row then back to just a click till I quit trying.

I think I'm going to get a couple shim packs and try to space it out like 1/8 or maybe even 3/16 just to see.
I'll update if I get any notable results

Since it is happening with two different starters it is less likely that the starter is the issue. If there is an inspection cover for the flywheel you may be able to disable the ignition and observe the starter pinion operation while an assistant operates the ignition switch.

Yes, I have the cover removed currently.
Being 4wd I don't think the starter will come out with the cover in place.

When I had done that check previously I could see the pinion would just hit the side of the flywheel. I haven't checked the latest starter yet.

Also check all connections, that you are getting FULL battery voltage to the solenoid.....

Yep, all new cables and connections.
I'll double check, again.

Please check the flywheel , they wear out in predominately one spot.

Ok, back at it today.
Resting battery voltage currently 12.8. I'm using a Fluke 85 III just fyiAlso trickle charged battery @2 amp setting for about 48 hours
Resting voltages:.
Solenoid input to battery negative 12.8
Solenoid input to starter case 12.8
Solenoid output to starter case 0
Key on Solenoid input to case 12.5

Load voltages
Solenoid input to battery negative
Solenoid input to starter case while cranking 11.2
Solenoid output to case while cranking 11.2
Solenoid output to case with only click 0.5
Solenoid output to batt negative with only click 0.5
Solenoid output to batt negative while cranking 11.2

Installed 3 shim pack 0.120" and click is much harder to cause but still happened maybe after 8 or 10 tries.
Key on Solenoid input to batt negative after a couple dozen 3 or 4 second cranks 12.55

I forgot to mention flywheel looks great. Contact pattern is a little better than 50% engagement which is a little better than the original was 5 or so years ago.
No strange engagement patterns on the ring gear or pinoin.
Also, I expected to hear some noise with that much shim but when it's turning over it sounds fine.
That's nearly an 8th inch difference! And it didn't sound bad before or after.

Here's the latest.
I could not find any noticeable wear or damage anywhere on the flywheel.
Other than the contact pattern I looks new.
I put a dial indicator on the flywheel to measure any possible warpage.
The greatest difference I could measure was only 0.009".
So a bent or warped flywheel is out.

Any other ideas?
I was thinking of trying to set the starter as far back as possible to allow the pinion to extend a little further and possibly make more of a rotation before stopping flat against the fly wheel.
The only other thing I can think of is to tear down the new Duralast starter and install it into the OEM case as I still have it and never had any engagement issues with that starter.