It may fit, but with a caveat!
I checked on Rockauto and early '86 calipers don't cross-match over to '88-'91 front calipers. However, looks like a Trooper manufactured from 11/86 would have the same calipers. And if that's the case, I don't see why it wouldn't upgrade.
You might want to look up specs on the rotors. Other than the Gen II rotors being of larger outer diameter, the fitment (offset, rotor thickness, center hole i.d., bolt pattern) would be the same.
So check your driver's door tag, I think that's where the build date lives.
If so, you can query on "Big Brake" or "Big Brake Mod" and there will be a lot of threads. Basically you need calipers and rotors from a Gen II Trooper '92-'98 or so. IIRC '93-'98 Rodeo will work as well. You'll probably need different brake hoses because the newer calipers have the hoses attach at a different angle. Rodeo hoses seem to work but you'll probably have to experiment.
If you're junkyard crawling, be sure to grab a set of the inner brake sheet metal dust shields, they are hard to find and not cheap new. Or you're gonna have to cut up your existing dust shields to make 'em fit the larger-diameter rotors, and they probably won't be purty! The later-style dust shields just bolt right in and fit & look as they should.