If you go the conversion route, make sure that you get the control unit and the cowl section where the A/C comes through the firewall. Also make sure to get all of the underhood lines and brackets. If your car has the 22" radiator, you'll need to swap over to a 26" radiiator. To do that and make it look stock, you'll need to replace the two radiator core support panels. Don't replace the top cross member as that should have you VIN stamped into it. Vintage makes a retrofit under-hood kit for those using the stock box and controls. It consists of a Sanden compressor, brackets, and hoses. Their kit for heater cars is very nice and very complete and you can even use dash vents. Scoring the 3-speaker A/C dash is nice, but for those who want to do the conversion from a heater car, Just Dashes will restore your dash with A/C vent provisions. I also assume that they can put in the holes for the outboard speakers. As far as I know, the metal sub-frames are all the same.
From someone who is doing a factory A/C conversion and used to work on cars (including A/C systems for a living), I would only go the factory route if you REALY want the complete look of a factory setup. Remember, you don't have to use underdash vents with the aftermarket systems. They look great and work great. Also, don't tackle the project if you don't know how to weld or if you think that going the factory route will save you money, because it won't.
