Yes it can be done. However, you will spend lots more than $ 200 before the job is complete. On the plus side, the installation will fit as if it came from the factory as opposed to being an aftermarket bolt on.

If I were doing it at this point, I would install all the parts (the dashboard with vents, condensor, evaporator, compressor and mounting bracket, wiring, switches, thermostat and any pulleys which may need to be changed. Unless prepunched, you will also need to drill and cut a hole in the firewall through which hoses pass from the engine compartment to the condensor. Get this hole lined up properly so hoses will have a straight route to the condensor attachment points. You may want to consider installing a new or refurbished compressor rather than one which is already 30 years old.

Then I would take it to an air conditioning specialist who could fabricate hoses, install any nipples etc needed to run the system on the newer R 134a refrigerant, supply a new dessicant canister, perhaps a compressor, and charge it all up.

I added AC to a 1971 140 series years ago before R 134a came into use. The parts came from several cars at a junk yard. I just poked around until I had one of everything. The system worked but was never as efficient or cold as what you will get now with R 134a......and maybe a new compressor. So bottom line, it can be done but $ 200 is far from the bottom line cost.