There are a couple of options.
1.) Vintage Air sells a kit for non A/C cars utilizing the existing heater box unit and adding the evaporator unit, plus controls. About $1500+/-.
2.) I have enough spare parts for the factory style (evaporator/heater core box), some dash vents, and control panel. You'd still have to purchase the engine compartment items (compressor, condensor, hoses, crankshaft pulley, and brackets. (Vintage Air about $900+/-) This option may cost a little more, but you'd then have a factory installation. The factory box I have is in good condition but would need a new heater core. The evaporator is good- just would need to be flushed.
The Vintage Air kit gets good reviews. It just depends on how original you want to be.
Neil