Our 93 truck, the heat valve is MIA. I found the broken valve in a box of parts the previous owner gave us. The heat valve was replaced by a copper tube. I just want to make sure we get it hooked up right, and so I can test the right port before we purchase the valve. There are also 2 vacuum ports on the firewall, that have screws stuck in them. I'm not sure what they go to. I would assume the older trucks are setup pretty much identical, but I don't know how far back.