I have a 1979 K10 with a 1984 cab on it. The cab is an A/C cab, but everything is missing from it to run A/C. My question is, can I take a heater box, fan, and heater control switch from a 1978 C10 and put it on the '84 K10 firewall. I notice right away that the heater core hose come out in different locations, and obviously the A/C fan box is much larger than the heat only fan box. The reason for me doing this, is I don't want to spend the money to add the A/C if I don't have to. Especially since I have everything else from another truck to eliminate it. Thanks in advance.