The Sanden 508 is available with the R-12 service port if you want to stay with original freon. If you are updating the compressor you may want to go to the more environmentally friendly and readily available, R-134. If you do, you may want to replace the condensor with a modern cross-flow condensor to make up for the lower efficiency of the gas. Either way you go, you should replace the dryer too.
For mounting to the existing bracket, the York to Sanden adapter is about $35.
Ray
'68 280SL 4-spd Coupe