How much trouble would it be to convert the kid's 85 2.5 from a carb to TBI ? This is our first 2.5 and we don't know squat about them. But trying to learn.
Get a donor Jeep park it next to the other and start swapping parts. Although I'd probably go with an MPFI just to get away from all those vacuum lines and gain an additional 12HP.
Probably easier to just pull the engine and drop in a MPFI in there then all you have to do is bring over the engine harness and PCM. You would need to add an inline fuel pump but that's not a big deal. You'll then want to use a OBDI speed sensor on the transfer case to get the correct speed to the computer.
You could go with a TBI but it's going to be just as much work of not more and for a whole 10hp. You could probably squeeze out that much with a carb swap ans some other mods.