I did a ton of research before I committed to the swap. After all it is a pretty significant undertaking.
I got my info from a lot of places. Novak was a lot of help, but there were things I had to figure out on my own or get the help from someone else. Like Mitch said, the motor is the cheap part of the swap.
I retained the AX15 that was behind the 4.0. Lots think I'm crazy and that I'm going to have problems, but I don't think I will. Every AX15 that I have seen fail is bearings and synchros. They seem to hold up well behind strokers too. If you buddy has an auto, I'm sure he will want to keep it auto. This presents a couple problems that are pretty easily overcome. First, he will need to get an adapter and output shaft for the GM trans. I would recommend a 4l65e. This is a great trans, electronic control, overdrive and a 4 speed. It will probably be a little longer than the current trans config, but since the motor moves forward in the conversion, he probably won't lose much, if any driveshaft length (I gained about 3-3.5" of driveshaft length). The other thing to consider with the auto is the console shifter. I do not know if you can make the stock Jeep one work or not. You would probably have to get an aftermarket one. Art Carr or Winters and Lokar both make good ones.
If you want to get technical with laws, federally speaking it is illegal to put any motor in the vehicle other than what it came with from the factory. That said, it is very easy to get a Gen III motor to pass emissions in Salt Lake county. You have to retain all of the EVAP system and have 2 cats (one for each cylinder bank).
As to what notajeep said about gauges....I have the stock TJ cluster and all the gauges work just as they should. Novak has developed a signal converter that takes the GM tach signal converts it so the Jeep CANBUS system can understand it. It is a pretty slick system. However, in order for any of your gauges to work, you have to retain the Jeep computer. Being that your buddy's Jeep is an 05-06, chances are the computer probably controls a lot more than just the engine like in my 97. It would probably be a nightmare to make everything work right if you removed it. Oh and I figured out a way to make my check engine light work. Took a little thought and some soldering, but it works like a champ.
After the swap is done you have to take it down to the I/M tech center in Murray. They will inspect it and make sure all the required emissions control systems are in place and FUNCTIONAL. You can not just put them in for show and have them disabled in the computer. They will reset the computer to make sure their monitors don't go instantly "ready."
I have been averaging between 20 and 22 mpg and have approx 350 hp at the crank. And it puts a big fat grin on your face when mash the throttle.
Good luck. Let me know if you have more questions. I don't claim to be an expert, but I can help out some.
