On my 74 C10, I have removed all the ac hardware that was on the firewall including the evaporator. I also bought the ac delete unit for the firewall, to route the air from the fan into the heater unit under the dash. Unlike pickups without ac, the vents under the dash, operate using vacuum. Someone before I bought the truck, disconnected the vacuum supply from the resevoir on the firewall (passenger side). If I must use vacuum, anyone know where to hook a vacuum line for the resevoir? Better yet, how can I use the heater/defroster without vacuum? Thanks for your help. I'll remove the condensor next once I get the rest of the work done.