On this replacement 78 Royale. I replaced everything that did anything inside, and out. And the A/C compressor made that list. My Dash A/C now puts out a great volume of air, and is very cold. ( As a note. The 77-78 Heat/A/C was much improved over previous years.) I also like the fact that I now can pull the right valve cover with out pulling the stock A/C brackets off. Very simple to install except for the fact that you have to pull the original very heavy stock one off. Very pleased. A good Idea is to pull the old drier off. Needs to be replaced anyway. And use a large pipe cutter to open it up. This will give you an idea of past issues with the A/C system. Should be clean in a good system. Got the kit from Jim K at Applied GMC. As another note. I did flush out the oil that came in the Sanden. So I could use oil that is compatible with R-12. If you can't get R-12. Dura cool might be a good choice for you. Bob Dunahugh Member GMCMI