My 68 stock A/C system was changed to R134a and the POA replaced with one properly calibrated. But the system was not properly flushed and cleaned. I will be flushing with cleaner and blowing it out with Nitrogen this weekend. I hope to get most of the old oil out by flushing the evaperator and condensor, and using nitrogen to blow our the entire system. So how much PAG oil should I put back in?

11 Ounces. Make sure you do a GOOD flush. Remove the expansion vale. Isolate the evap and cond, then flush them real good. Since you have it open put a new receiver on it. Dont flush the receiver. Do good leak check and pull real good vacuum.

Stay Cool.

Service manual says total of 11 oz. Of course this is for a 12 system

Remove the compressor and drain it. That way your good to go with the proper amount.