I know this is an old old old thread but here it is anyway...
1994 was the year of the big CHANGE.....
As part of the MONTREAL PROTOCAL federal law said Automakers were to phase out
the use of R-12 as a refrigerant in cars by the model year 1994.
So having said that, ANY 94 and newer car\truck etc will be 134-a, and usually
any 93 and older car\truck etc will be the old friend R-12.
Bigtee