A suggestion. Use a new rotary compressor. The York compressor that came with the dealer installed AC in a 914 was a horsepower hog.
I used a compressor replacement kit from Iceac (
http://www.iceac.com) It was very complete, and it works great. It comes with a new pulley, a v-rib belt, the mounting brackets, the compressor, and all the bolts and nuts necessary to install it. It also enabled me to do an R134a conversion on the car. We have had it working for 2 years now without touching it. On a 100+ degree day in Texas we have to turn it down to keep our teeth from chattering.
Good luck.......