Has anyone ever done this? Its a 1x11.5 thread, GD has a die that I can use and send back but I was wanting to buy one for chasing and cleaning my threads later.

Yes.

Not much to it.
Are u looking for "how to" advice? Renting tools from go devil? Buying die yourself?

Not sure what input u are looking for

I was wanting to buy a die to keep but all of my google searches are coming up empty. I will probably just borrow the 1 from GD.
I guess I'm looking for the degree of difficulty for this task and any tips/tricks that will make it a successful operation.
How big of a difference are the threads? Will it be kinda like chasing the threads while cutting a little steel with it? GD also said to do it with the new bushing installed. Not knowing exactly how it works, my concern turns to getting the die square and started in the right place on the bushing allowing it to line up with the threads on the shaft housing.
Am I over thinking this crap? Do I just beat the bushing in, run the die up and let it ride or what?

Tap the bushing in, insert shaft, check for binding, reassemble, and roll. I've never had to retread or chase anything with the newer style assembly.

I have a late 80's unit. Since then, they have changed the threads and I got a new cap/seals. That's why I have to rethread it.

Gotcha.

I'm pretty sure the threads are the same. If they changed pitch it would cut into the threads already there making for a weak joint. You might want to double check on that.

GD said that is what I need to do to make it fit and they will send me the die for a small deposit. So I assume that it is standard practice for the dinosaurs.

Good machine shop tool houses could fix You up with a die. One that big made of high speed steel and american made is going to cost over $100.00 Foreign will be cheaper, and carbon steel will be cheaper still. I have used them all and now always buy the american made high speed steel ones. Try KBC tools. They are national and sell on the web, both domestic and foreign.

Mark F. Cheney