BY "freon" do you mean R-12? If so then the answer is no. The system uses 134A refridgerant and does not need to be converted.
Was built for R12, should be converted to R134a
Unless it has been converted to R134, the OEM refrigerant installed in 1991 was R12 Freon. I suggest you have it converted to R134 if it has not already been done.
The refrigerant needs to be added on the low pressure side of the compressor. this is located under the front of the vehicle by the bottom of the radiator. the line has a fitting which should have a blue cap on it. that's where you add the freon.
R134a
None, the refrigerant is R134a not Freon which is R12.
R134a
never use it
R-134
R134a
R134a
It originally came with Freon (R12). Unless it has been converted then it will still contains R12. I suggest you have it converted to R134a, as Freon is so very expensive and hard to find.
R-134