If properly maintained, 145K is just broken in on the 4.0L eingine!! I have a 98 Sport (not much left of stock sport left) and I have 153k and it's fine. Just maintain it, regular oil changes, and that 4.0 will last for 250k+. I've seen it in TJ, YJ, and XJ...
You search around, you can get an 8.8 and if you have a buddy that welds, you can mock it up and get it done cheap (relatively speaking). Just determine what you want to do, what the ultimate end-goal is, and work towards it. That's what 99% of us Jeep owners do and it's just the means to an end.
JEEP = Just Empty Every Pocket!!!