Sort of like yelling "fire" in a crowded theater, and I hesitate to feed yet another 'alternative refrigerant' thread, but I would strongly suggest sticking with the r-12.
Freezone is some 80% r-134a mixed with some r-142b. 142b is an HCFC and an ozone depleter, and is scheduled for phaseout in 2010.
Looks like it still costs about 1/2 as much as r-12, so how much are you really going to save?
1986 300E 5-Speed 240k mi.