I'm sure what I did is technically not perfect, but it worked for me:
1. purchased a R143 conversion kit that included freon, gauges, R12 to R134 fill adapters, instructions, etc...
2. Removed the covers from the R12 caps
3. Installed the R134 converters
Note: when looking at the compressor on my '87 from the front of the Jeep, the low pressure side is on the right.
4. Attached the gauges to the low-pressure side of the compressor (I had to trim it a bit to get it to fit.
5. Disconnected the low-pressure bypass switch and ran a jumper from one side of the plug to the other.
6. Took the cap off the low-pressure side valve (should have a rod sticking out with a squared-off end.
7. Opened the valve of the low-pressure side of the compressor by turning the square rod clockwise (it is reverse-threaded)
8. Turned on the engine and set the A/C to normal
9. The compressor and clutch should be spinning - you will be able to see the front of the clutch spinning if everything is OK. If not, you need to troubleshoot an electrical or clutch problem.
10. Added 45 lbs of freon making sure to watch and listen for problems.
Note: If you need to swap cans of freon, make sure to close the low-pressure valve on the compressor (by turning counter-clockwise since it's reverse-threaded) before disconnecting your filling system)
11. Checked the cabin and voila! Cold air.
12. Removed my low-pressure cutoff bypass and checked to make sure the switch was still working (once connected , the aux fan should kick in)
13. Closed all valves, installed all caps, buttoned everything back up, checked for misc. tools and parts left in the engine bay, and claimed success.
14. Drove around town with the A/C on full blast to "check it out"
15. Came home cold and happy.
Time will tell if there is a leak anywhere, but at least none of the major components were faulty (that may change).
Total cost was around $40 and it took about an hour once I had my headgear on straight.
BTW, this forum has helped me so much, I had to join. I know I've saved way more than $35 in mistakes, delays and frustration.