I had a tired 4 liter also and decided to go with a 350. The only thing I had to really do was the engine mounts and an adapter to the trainy. I would swap out the automatic for a standard, you would have more control over what your jeep will do. If you do that you can get a direct bolt trany transfer from a chevy that would be a good upgrade. Going with a v 8 will give you more than 1 1/2 times more horse power and tourque with just a plane 350, for a little more you can get a beast of an engine that won't quit. Mine has gone over 250 degrees several times and is still as good as new. Of course I use the top oil, AMSOIL ZROD. If you go that way you will have to make sure your water pump is high volume and have at least a three core radiator.