Far as I know, all is the same, at least as far as Fox-bodies are concerned. It wasn't until automakers started using R-134 in the early 90's that things got a little different, although nothing dramatic. You can always retrofit R-134 into an older 5.0 just by flushing the system out completely, putting on the different R-134 fittings, sucking it down, and pumping 'er full again, although it would be a good idea when you do that to swap all the A/C system seals out with newer-style O-rings and such. And, of course, you ALWAYS wanna replace the orifice tube and accumulator when redoing the A/C system, as they kind of act as filters to screen out all the gunk n' crap, and they tend to plug up over time.
I don't think Ford really started using R-134 all across the board until around '94 (or '96, at the latest), so pretty much all '79-'92 Foxes were R-12 from the factory ... not so sure about the '93 models, though.