Anyone done Under Dash A/C ?

I bought a vintage knee-knocker on ebay (~$60) for my 64 Valiant. I don't know if any are "correct" since installed by dealers, K-mart, Sears, Western Auto, ... There was a Chrysler "Air Temp" brand or such, which might have had an under-dash version (forgot). You can buy new ones for $100 on ebay. Slicker is the Classic Air "behind dash" unit, which replaces your factory heater box and routes tubes thru a plate where the blower motor penetrated the firewall. A factory system won't exactly fit since the firewall was different in AC cars.