Hello, its my first post in here.

I hope some one can help me with my AC issue.
I have a w126 300SEL 1988 M103 engine, 3 years ago the previous owner converted the car to 134A at the dealership, new denso compressor, expansion valve, suction hose. in Texas heat i am getting 55F at night from the center vents, 70F during the day. the AC is just not there and not doing anything. I found a good deal on R12 freon and want to convert back, I also asked my bud to make aluminum P-condenser for me with brackets, also I picked S70 volvo 3100CFM fan to delete the mechanical fan and convert to electric.
Can someone help me what do I need to do to convert back to R12, already bought new drier and expansion valve. how to flush the system, drying time after flushing, compressor oil, are the green seals compatible with R12 ... etc.

Appreciate any comments