Thought I'd start a new post instead of going off the old one about selling my Toyota. How big of a tire can I fit on this truck without lifting? I do intend to lift it but I'll probably do it at the same time. I'm hoping to fit 32" tires but I don't want any rubbing issues. Also, I think I'm gonna have to change the front CV joints, fun. Any thoughts? Thanks.

Troopers have big wheel wells, you can fit 265/75s (~32") without any lift. A modest lift will get you 285/75s (~33").

The CVs aren't bad to change if you just do the outer part (pull apart the inner joint and swap the outer part). Best to use junkyard CVs for that. And if you take off the drive flanges and install manual hubs the CVs won't get worn as fast, and you might pick up half to one mpg.

Otherwise, replacing the entire CV all the way to the diff is a LOT more work, you basically have to drop the whole axle.

Great info. 32"s won't rub? Even turned hard? That's cool. Some ground clearance would be good. I'm gonna remove the running boards, are they worth anything to anyone here on the forum? I can't ship them but I'll drop them off to anyone within 25 miles of zip 92867. SoCal. Gonna build a roof rack as well. I have a great plan.

I used to have a 99 Trooper. I had a very mild setup: 1" lift (OME 912 coils) and 265/75 tires...plenty of clearance.

Here I am wheeling the Elephant Hill trail in Canyonlands National Park in Utah.

Wheels make a big difference on what size tire fits. The stock wheels allow the biggest tires. A 33" tall tire fits ok with the stock wheels, but a 33 12.5 15 on your regular 8" wide rim will not fit. So to maximize the space you should stick with the stock wheels or use wheels with the same back spacing as stock.
I made 35 12.50 15's fit on my '96, but had to cut quite a bit out of the front fender towards the rear, the plastic flairs cover up most of the cutting, but the stock mud flaps had to come off. Also I had to flatten out the fender lip in the rear, but the plastic flairs hide all of that work. The only rubbing I had is the pass front tire would rub the washer fluid resivoir when hard on the bump stops, like when jumping.
Unless you add a body lift it will make no difference how you "lift" the trooper. The same size will fit at stock height.
I would agree that the OME 912 coils with a mild T-bar crank is the best option. Be aware that the front tires tow in as you lift, so measure the tow and make an adjustment as needed.