Well i was gonna suggest a dakota rear as its only a lil wider and will bolt to the factory dprings
But then you mentioned the bolt pattern
Bolt pattern's not a problem with an '87-'90 rear. Only '91-'04s were 6 lug.
I'm at the point where I have to decide to put money into the 7.25" axle for my Valiant. It's noisy. But the only other choice is really an a body 8.75" which is really expensive. Or to swap to big bolt pattern and waste the money I have invested in small bolt wheels.
I hate the 7.25" axle. Have I said that before
What's become popular are the Explorer 8.8 swaps (cheap, disc brake rear with LSD and steep gears, yoke is offset unless you swap axles- which can be done cheap using Aerostar parts I've read)
The other thing is just using a '66-'70 B body 8-3/4 rear end with the perches moved .5" on either side inboard- which I can't see why you wouldn't as opposed to upgrading to the A body rear. Or door number 3, use a donor '73-6 car for the front spindles, UCAs, and rear 8-1/4.
5x4 isn't worth keeping unless you have the small bolt early Mustang-style K-H discs and want to run 13" wheels. And it's probably not worth keeping then either.