Fill in your profile: Yr, engine, trans, 4 or 2 wd, package (sport, pioneer, Laredo, etc.), and you location. I know you put it in your original post, but that will scroll off the screen in no time.
Welcome to the addiction
You need to check out the thread in the DIY section. SCJ Steve has a discussion on Key Parts floor pans. He also has a U-Tube channel where he is refurbishing his MJ.
You can search your area for a company that does electric motor rewinding. If they can't help, they may know a company that can.
Good luck. I have a DeWalt radial arm saw that was my dad's. As long as I can remember, it was in our basement. I was born in '64, so it is probably sixty years old or more. It still works fine (for what I need from it).
We need more info: engine - 4 or 6 cyl, transmission, etc. Complete your profile. (Also, your location: City, State/Province)
What, if anything, have you tried?
Welcome to the addiction.
In order for you to help diagnose the Renix engine you should get two things: 1) The Renix engine control manual, and 2) Nickintime's REM module.
Both of these will help you.
The MR277 come in two volumes. The first 1.5 books covers the 86 model. The second half of vol. 2 covers the 87 4.0 model, technical service bulletins, and other updates.
If it "cranks," then it is turning over. If it "cranks" but doesn't "start" then that is a "crank, no start" condition. Now, you can start with the fuel and spark issue.
Search for Cruiser's Renix Tips to assist with diagnosing some common issues for Renix engines. Test the CPS (been there, done that). Get a fuel pressure tester to make sure there is adequate fuel pressure. These can be "rented" from most auto parts stores.
Next, perform many of the Renix Tips as prescribed by Cruiser.
I put a 93 XJ 4.0 in a CJ7. I pulled the engine wiring harness and the ECU to do the install. On the CJ forums, there is a rule "Five Wires to Fire." That means that just five wires from the "new" engine wiring will connect to the "old" wiring. I don't know the number of wires for the Renix system. You most likely would want just about everything from the 93 to install in your 87.