These may seem pessimistic, but in fact they’re realistic.
1. Just because you have an engine doesn’t mean it’s a good engine swap candidate.
2. The Rule of 2: It will cost twice as much, take twice as long, and require twice the radiator to cool it.
3. Just because you have a good-running foreign engine doesn’t mean it’s right to put it in an American-made 4x4. Yes, it has been done. Yes, they run great. But it’s just wrong. Ask any old guy.
4. A Jeep 4.0L is a great engine in whatever it came in, but not good enough to swap into something else (not even a four-cylinder Wrangler).
5. If the vehicle you are building is already available from a manufacturer, just sell your project and buy one. It’ll be cheaper. (This also goes for 2x4-to-4x4 swaps.) For example, see Rule 4.
6. You will need custom exhaust to make it work and fit well in the framerails.
7. Before you remove the old engine, take pictures and mark every wire and hose.
8. Don’t be scared of fuel injection if the engine you are swapping in has aftermarket wiring harnesses available (e.g., TBI GM, 5.0L Ford, LS series GM). But be afraid of trying to make a junkyard fuel-injected engine run with the original wiring harness — it’s like sorting spaghetti.
9. Oil pans can cause problems with front axles. Driveshafts can cause problems with starters. Keep this in mind before welding in motor mounts.
10. Swapping to a diesel engine will cost more than you will ever save by the fuel economy of driving a diesel engine. It’s cool but not necessarily economical.
11. GM V-8 swaps are boring, but there is a reason everyone does it. The cool unusual engines are expensive to install, fix, and keep running. And love them or hate them, GM Gen III and IV LS V-8s are great engines for four-wheeling.