I have a DPD system installed on my wife's 914. In a 100+ Texas summer day, we have to turn it down to keep our teeth from chattering. The car came with AC, but I did a R134a conversion on it after the engine fire. I replaced all the lines, the dryer, all the o-rings, and I used a R-134a compressor conversion kit from IceAc.
http://www.iceac.com The kit was worth the money, it was a true bolt on. It comes complete with the compressor, and all of the necessary mounting brackets, bolts, and pulleys. The system has been working for 3 years now, and has not required any maintenence at all.
If you need the official installation manual for the AC, contact Jon Lowe. He is the PCA 914 tech expert, and he has copies of the manuals.
Hope that helps.