Most 37's will fit, however some of the bigger tires like the maxxis and pitbulls may be pretty tight since they seem to run a little bigger.
If I did it over again, and I may later down the road, I would have waited for the un powder coated (bare steel) fenders and cut the rears to add another few inches to the wheel well. That way you have clearance for a 39.5 and or can move the axle back a little more
The 37's look good, but to me they look small now, kinda wish I had 39.5's, but that would require way more than I want to do to a Cherokee....
I'm building a hp 44 for the front and may pick up a 44 for the rear down the road. My main concern right now is getting my frame stiffys on and doing the 2x6 rockers and getting bumpers on finally. Then I need to start a cage