The 2.3L wiring harness will not work. This one is making my brain hurt a little.
What transmission, auto or manual? I would say that the 1988 Ranger main harness and computer would be your best bet as far as plug-and-play. Reason being is that the 1988 model year did not have factory EGR. I am not sure on the specifics, but I know 88 had computer controlled O/D, I keep thinking '87 and older was not (computer might throw a code worst case).
'89+ was a generation switch and there are some significant differences in the wiring. Not that it's impossible to wire a Gen-II harness to a Gen-I dash, just that it's going to be somewhat of an effort.
But it would be possible to use a 86-88 2.9L main harness, just the 86-87 would have provision for EGR and there might be a couple of minor wiring issues to sort out if used with a 1988 non-EGR computer. Or could try to get the EGR system in tact, but then again, I wouldn't put myself through that (or deal with all of the EGR codes and rich fuel mixture using an 86-87 computer with no EGR components).
No clue on the x-fer cases, will have to do some researching on what you have or maybe someone can chime in.