[Dingfodgy]

I just did this mod a week or so ago, although I'm running the A/C delete pulley . It's not that hard if you have all the S.L.D.'s (S*#tty Little Details) figured out. You will need to get the WP with the Heater Hose provision. Mine came off a 89 or 90 S10 Blazer and had the provision, but I also have one off a '90 Astro Van and it does not have the little nipple for the heater hose. Also, make sure you either get the reverse rotation cooling fan or switch to electric.
Regarding the A/C question. The R4 Compressors that typically come with the J/Y Serp.Systems are designed for R134 and the 67-72 factory systems used R12. I don't know what it takes to convert, but I can't see it being too complicated. I'm sure you'll need new hoses made because I think the newer compressor uses different style / size fittings. And you'll probably have to do some minor wiring for the switches and clutch.