my car has not been converted yet and i noticed on ebay they sell r12 on there so i was wondering if i should buy the r12 or if i should do a 134a conversion? i have ac manifold gauges and a vac pump to evacuate the system (along with alot of other tools) so i was wondering what would be the best route to take? and if i do convert it what do i need to do on my 85 300td td to properly do so? and where are the ports? i know theres one right in your face when you open the hood but where is the other one?

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1985 mercedes benz 300D turbo diesel
1998 VW GTI VR6
1996 VW GTI 2.0
1999 saab 9-3 turbo
1987 300sdl (sold)