easiest...4.0...v8 requires a lot of mods....what r u trying to build? axles? tire size?
there's more to it that just dropping a v8 in it. there is a jeep in my crew with a stock 4.0 that can do anything the v8 jeeps can do and more.
in this video the red jeep is a v8 and the black jeep in a stock 4.0. both have 2.5 ton rockwell axles and 52" tires and pto wenches
more of the stock 4.0 jeep on 53" tires And 2.5 Ton Rockwells