Tim
It is not illegal to use in MA. It is however again the Clean Air Act if I replace an ozone depleting refrigerant. It is legal to replace R134a however.
No tech will touch my car and I will keep it as long as it lasts.
Pulling a strong vaccum might be easy with a good pump, but the loaners I have seen were in very poor condition. I am reluctant buying a new pump - I'll leave the country and would then need a 240V version. Versions that can use both voltages are 450$ or more.
I am not concerned about safety: less than 1lb of hydrocarbons are no big threat in the very unlikely case of a fire. It is certainly way much less energy than 20 gallons of fuel.
But let's see, I do have not decided yet. If I find a place with good loaner pump I will stay with R12. (Anyway I would have to convert to R134a first in order not to violate the law.) It is just hard for me to understand the polemic against the hydrocarbons.
Bruno