Depending on the transmission you have.  You could have an AX-15 or a BA-10. Costs will be much cheaper with the AX-15 since the transmission will match up and handle the output of the 4.0.

I did the swap on my 89 YJ Sahara using a 94 XJ 4.0, AX-15, and NP231 all from the same donar.  I also took the harness and computer at that time.  The motor had about 60k on it.

Key points I remember were swapping the motor mounts.  The XJ's were 1" thinner than the YJ's. Installing a E2000 fuel pump and return.  Don't forget to take the exhaust manifold for the oxygen sensor.

Last was the wiring I got most of my notes from the 4.0 swap thread on cjoffroad.com.  It took one weekend to pull the entire drive train, swap it the new one, and then wire it up. 

Now the YJ starts every morning and I never have to hear that nasty "carb" word.

I have the AX-15, thank God.  

You did it all in one weekend?

Has anyone done this swap but maintained the older style induction?

Is it even possible to do without using the fuel injection?  Since the computer for the ignition also would control the injection, it may not be possible to separate the two functions.  A programming whiz with the proper equipment might do it...  

I agree. a complete donor would probably be the cheapest way to go.

I'm sure you could set up the 4.0 head to run a carb or the howell (its TBI right?), but the OEM style MPI is better.

I put a holley 390 on a 2002 4.0 using a clifford intake and it runs great.  I got the complete 4.0,nv 3550,and 231 all from the same TJ.  I went with the carb because where I plan on going I do not want to take the chance of troubleshooting electrical components in the middle of nowhere.  

I just bought a 2000 TJ with the 4.0 L I6. I plan on using a propane carb. Will disconecting all the electronics and adding a distributor work. Any advice would be helpfull. Thanks