Would the 4x4 system on a 1987 Ford Bronco II be a nightmare and a half?

1987 would've been right about the time where Ford came out with it's push-button "Touch Drive" 4WD engagement system. The early iterations were not reliable at all and they indeed had a tendency to randomly stop functioning. Oddly they failed mainly because of *lack* of use. But if the Bronco II you're looking at has manual hubs, then the 4WD system should be pretty bulletproof.

I had Touch Drive on my 1995 full sized Bronco, and even though it was one of the improved later versions, it would still not engage 4WD consistently. The electric motor that engaged the front drivetrain on the transfer case would seize up. The quick fix involved sliding underneath the vehicle with a hammer or large piece of wood and hit the electric motor a few times whilst you have a buddy sit in the truck and constant push the 4WD button.

The Bronco II's as far as I know all had manual transfer cases. This means, you had to manually pull a lever to engage or disengage 4 wheel drive. There's nothing to fail on it, it's just a manually actuated chain driven transfer case.