Okay I'll give it to you that I'm downplaying the ax-5 too much...
But as far as I know, the ba10/5 never came behind the 2.8, only the t-5 and ax-5. The pukegoat was used only behind the 4.2 and 4.0 from 87-89. Note that the 2.8 was phased out as the wrangler, 4.0 cherokee, and ba 10/5 were introduced (87). I'm not trying to argue, as all information sources are subject to fault, so I can't be sure. I've read a bunch of different factory and aftermarket manuals, and they rarely perfectly agree.
Well, I did some more researching. The transmission on the 2.8L is probably an AX-5. The T-4 was only used with the 2.5L in 1984 only. The T-5 was the used with the 2.8L in 1984 only as well. In the OP's case, if he had to get an AX-5 I'd get one from a late model TJ so it will be newer and probably have less mileage on it.
Haha, remember we're considering tranny swaps, not engine? For the record, 86 will ONLY have a non c-clip dana 35, 87 was the first year of the XJ 44 (once again, that crucial year when chrysler bought amc, but amc hadn't lost its' identity yet).
I can agree, though, that the nv3550 is the best option if he wants to do a little bit more than JUST a 4wd swap.
The 1984-1990 Dana 35c's will all have no C-clips. They are easily spotted by their 10x1.75" vented drums. The switch to 9x2.5" non-vented drums and C-clips came in 1991 with the first big update.
In any case, like DodgeMudder, said, the NV3550 is pretty much the same for the AX-15 as they share the same bellhousing bolt patterns and output shaft spline counts.
OP, here's a rundown on Dana 30's for XJ's. It still fails to mention which ones have vacuum disconnects. So, just be aware of that when looking. They're easy to spot anyway. Strange that they also mention the 297x U-joints being a 1996 thing. Typically, XJ's have changed over before the YJ's and the YJ's received the 297x's back in 1994.
* 1984 – 1996 : Dana 30, High Pinion, Reverse Cut, 27-spline axleshafts (1989 – 1995 : with ABS used 5-297x universal joints, non-ABS had 5-260x universal joints. Note: Certain XJ models were produced with constant-velocity joints instead of universal joints.)
* 1996 – 1999 : Dana 30, High Pinion, Reverse Cut, 297x/760 universal Joint, 27-spline axleshafts.
* 2000 – 2001 : Dana 30, Low Pinion, Standard Cut, 297x/760 universal Joint, 27-spline axleshafts.
Although, like I said before check that 2.8L for a Dana 44. You'll have to regear it but it's well worth it if you're planning on larger tires.