Pictures would help. I'd either go with an OM617 or turbo the 616 and get a pump from Dieselmeken - the 616 ought to make lots more power than you'll need if you do that. I don't know how much room the Jeep chassis has for the 5th. cylinder on the 617 but it WAS a tight fit in my S-10.

Other than working out the length, the 617 would be basically a bolt-in in place of the 616. You might need a tad more radiator and you'll have to move the mounts to fit where you need them - current location might be OK. IF you can keep the trans where it currently is the clutch linkage, etc. can stay as it is making the swap that much easier. If you can move the rad forward about 8" or so the engine ought to fit in the space from the bellhousing forward. I don't run the engine mount shocks and have had no issues with that.

BTW - a stock 617 turbo is more or less 125 HP and can be modified to considerably more if you get power hungry later. It sure is worth considering.

Dan