So I take it you're looking to drop yur truck right down to the asphalt? Make er' lay frame prolly? I read up on doing this (cutting the frontend off and putting Mustang II stuff under it) a long time ago when I had 2wd Ranger.
Just off the top of my head, a few of the MAJOR issues you will prolly run into are:
-hooking the Mustang II crossmember/subframe up to your Ranger's frame
-setting up some sort of engine mounts in the new Mustang II frontend
-creating a system for mounting up your body to the new front frame.
-setting up the radiator in the new subframe
-the steering system..(I think a 79-93 Mustang rack and pinion system will work)
those are just a few things to think about before you get started.....disregard this if you already know this stuff, but since nobody had chimed in yet, I figured this might help ya out.
If you could get that thing sittin right down on the ground, that'd be sick.....with the 1/4 panels like a 1/4" above pavement......