Are you going with R-12 or R-134a? Are you planning on replacing the hoses, too?

I have rebuilt the AC systems in many classic cars and I always replace the compressor with a Sanden rotary, I replace the original condenser with a parallel flow condenser (almost always less than $100), I make a new set of barrier hoses, and I replace the receiver/drier and the expansion valve.
My experience has shown me that when all that is replaced, R-134 cools the vehicle perfectly. My current project is a late 1970s BMW 7-series and I am getting 38* degree air out the vents on R-134.