I just finished doing a swap myself although it's still not finished - I have to install a radio, put some more bolts in the dash, and cut the window for the defrost. I'm not sure if I'm going to do the defrost. I've driven it in the snow and haven't even needed it yet so I may not. I bought a CJ dash off Craigslist for $100 and used all the old gauges. I learned a few things along the way and can probably answer some questions. My YJ is a 95 and I used wiring diagrams I found online and from a Chiltons manual that is for 1987-1995 Wranglers. I know most Chiltons cover multiple years/models and usually aren't very good. However, the one that is only YJs was spot on for the wiring. I didn't have a CJ harness so I built by own using weatherpak connectors - they are a bit pricey and you could probably use the multi-pin molex connectors from Radio Shack.
One challenge was how to hook the cables for the heater, vent, etc. First I removed all of the old YJ cables. If you search some forums you'll find the door that is operated by vacuum is only closed when the old lever was in the "off" position. I decided I would leave the vacuum hooked up so it's open whenever the engine is running as I like airflow anyway and I can still control the temp. I ziptied the vent door that is behind the steering wheel up under the body behind the dash - mostly because mine never worked correctly with the old levers and I thought it would just be too hard to mess with. I connected the temp door, defrost deflector door, and the lower vent door using Dorman Help universal cables from O'reilly auto parts - the ones with 1" chrome knobs on them. I found that once you remove the yj cables you can carefully "unthread" the plastic adapters that hold the cables in place to the YJ components. I simply cut the Dorman cables to fit and "threaded" the plastic connectors onto the Dorman cables. They all work like a champ with the exception of the temp control being fairly stiff - which it was before the dash swap too. For that cable I added some additional cable terminal ends in case it trys to slip. Oh yea, and the temp control is opposite of what the CJ dash indicator/label states. Overall I'm really happy with the function and look of the cables.
Using the old CJ gauges I had to replace the sending units. The temp and oil pressure sending units are super easy to change and they fit. It can be frustrating finding the right sending unit for your oil pressure gauge however. If you search some forums you'll find there were several gauges/sending units throughout the years and I didn't even know what the dash came off of. I have not changed the fuel sending unit yet so my gas gauge reads backwards (F is empty, E is full).
Yea, that's pretty much it. Use the 91' VSS that has both a mechanical connection for a speedo cable and an electrical connection for your VSS.
To use it, you'll require a speedometer pinion gear housing assembly. I got lucky because my neighbor had one in his garage! You will need to find one somewhere as that is what the VSS screws on to.
Also, the VSS has a 5/8" speedometer cable connection - the same as the back of the CJ speedo. The speedometer cables I could find are typically 5/8 on one end, and 7/8 on the other. So you can either get a custom cable (pricey) or find a 5/8 to 7/8 thread adapter. I was able to find an adapter online and order it (like $6 for the part and $6 for shipping). I'm sure you could find something similar at a junkyard if you did your homework.
How did you guys do the headlight switch? i'm looking at the diagrams for yj and cj switches and can't figure it out. I want to retain full function of the switches, which i would think is possible. Any hints, tips, or help? Thanks