Plan on doing a lot of research, especially if this is your first swap. Engine choices are plenty, but I find the three most popular choices are the Chevy 350, the GM LS1, the Magnum 5.9L (difficult to find), and the 4BT (beastly).
I haven't seen too many 302s, but I know a lot of people are fans of Ford swap I just don't know any builds off the top of my head.
Novak is your first valuable source. They've got the custom engine brackets and know-how you'll need to begin, but it's really just a jumping off point. From there, you need to consider your axles (NO D35, D44 still isn't great), fuel pump setup, the transmission, the radiator, the exhaust, getting a custom flash ($$$), proper wiring, fitting everything (may require a body lift), and even after planning for anything and everything, plan on still spending a while tuning and getting the final adjustments done. I've seen a few great builds end with the owner curbing their Jeep because it just never ran properly.
I'm now in the planning phase of mine. I am mostly likely going LS1 given the custom options and repair resources, but my biggest fear is proper wiring.