remotemark,

Reverse conversion is not that difficult. I would not suggest doing it on a working, converted system, but when it comes time to make a repair on the system and the refrigerant is being recevered anyway, simply do whatever repair is necessary, flush the system, replace the r/d, put in the correct amount of Mineral oil, evacuate and charge. There are now some synthetic oils that work quite well with R12. It would be a good time to go to one of those products as the lubricant in place of the mineral oil.

I have done several reverse conversions with great success!