Actually the newest versions of the R4 compressors are different than the original ones. They use different seals at the fitting assy and have a different clutch. Matching the numbers won't work AND if you buy it at NAPA it probably won't have the Delco Harrison (now Delphi) numbers anyway. For that price you are buying rebuilt. I would go to your nearest A/C Delco Jobber and buy a Delco/Delphi# 15-20206. This is a brand new unit (current version) and should be available for $2-250. For that price it is silly to use a rebuilt.