[454HO]

If you ever anticipate an a/c service shop will work on your truck in the future, then either stick with the good old R-12 or the only EPA approved replacement R-134a. Most shops won't touch anything else. Their refrigerant recovery equipment is normally dedicated to either R-12 or R134a. Anything else will cause it to become 'contaminated' and will cost BIG $$$$ to deal with. Also remember that a/c compressors, as well as many other a/c components, are usually only warranted if they are used with R-12 or R-134a.

And those enviro-friendly alternatives you mention are probably hydro-carbon (as in propane) blends. There is a lot of hype about using highly flamable gases in an automotive a/c environment. Some people don't think it's a big deal to be riding around the streets with a relatively large quantity of highly pressurized liquid propane only inches away from them. Others think those people are totally assinine. All I can say is educate yourself and make a decision that you and the people around you can live with.