Denny,
There were only two GM accessory Heater/Defroster units in 1950 (late 1949-1950). The "Outside-Air Ventilator, Heater and Defroster" (this does not have the cable-controlled door on the front face - the cable controls the defroster in 1950); and, the "Dash Reciculating Heater and Defroster Unit" - this is the more common, less expensive unit that has no cable-control and has a deflector-lever on the body of the unit, for the defroster).
I will post scans in a few hours of the original 1950 heater/defrosters and original price list.
Most likely you will still not be able to see things at my website (same problem as in other thread). Try the link below and please send me your IP address (ignore the rest of that page).
I am very sorry about the pop-ups from the other link - I have my web browsers set to block all pop-ups, so I have no idea of which sites use those obnoxious features. The link below will have no pop-ups (but, ignore the stuff at the bottom of the page).
Please send me the IP address. Tim
lederman@siena.edu