You probably have some old/bad O-Rings that caused it to leak out. Replace all of your O-Rings. They are cheap. Replace them and go from there.

As of now your R-12 (Is VERY EXPENSIVE and TOUGH to get) is probably over Australia by now. I got the last of what we had at our dealership. I didn't pay anything for it. Thank God... More than I would want to pay for it.

If you want an exact replacement get some Freeze-12. Put this in your ride. You should not have to do the conversion to R-134. The Freeze-12 blows colder than the R-134.

Good luck!