Re: deisel swap
There was diesel versions here '99-'01 had the Detroit Diesel 3.1 lump and '02-'04 had a Mercedes Benz 2.7 lump which was a huge improvement and responds pretty well to tuning - check out the Export section.
The cost involved of swapping one of these into your Jeep (and importing it and all its accessories) would be ridiculous though.
"Even though I walk through the valley of the shadow of rice, I will fear no turbo for thou torque art with me. Thy rods and crankshaft, they comfort me."