R-12 freon to sell, how?

There's no reason to use r-12 in a car, to convert you put an adapter on the lowside, evacuate, pull a vacuum, charge with r-134 (3/4 or so what you'd use with 134) add dye and you've converted it. For a concourse look, unthread the adapter and replace the old cap.

But, one of those 'if you can sell it' things