how much trouble to put ac back on?

i have a 73 valiant 4door that im making my daily driver and last year after having probs with the engine i took off the compressor and drier and condensor from the ac that didnt work. the lines connections going into the dash were left open and i was wondering what i would need to get this back on and in working order or would i be better off trying to get and aftermarket system e\ven though the car already had air from the factory. thanks:read2: