The A/C Condenser is one of the major components in the air conditioning system. Like a radiator removes heat from coolant, the condenser removes heat from the highly-pressurized refrigerant after it’s compressed by the A/C Compressor.
A common upgrade for R12 systems (especially those converting their R12 systems to R134A) is to install an R134A condenser as a replacement. The R134A condenser features a higher fin density, making it more efficient in cooling.
Replacement is as simple as unbolting the old and installing the new, after removing the radiator. Be sure to properly evacuate any refrigerant from the system, and follow the guidelines on the A/C Recharge article.