:cheers: Welcome to the board.

Before spending money on refrigerant, I'd make sure that:
1) The compressor itself is still functional.
2) That all the lines and seals are good.

Once the system is in good mechanical shape, then I'd say go ahead and use the R12 substitute. There's little point in spending hundreds of dollars to convert to R134 on an older car, unless you're going to keep it for another 8 to 10 years.