[48richard]

I've been doing some research on aftermarket kits like Classic Air, Vintage Air, etc, and as far as I can tell all of them only cool recirculated inside air. The factory system in our trucks uses fresh air all the time unless the control is set to inside air, and IMHO that's the way to go.
I've taken paper patterns off a junkyard cab for the openings through the firewall and in the dash for the vents, and have made a parts list (fairly complete, I think!), using the factory service manual, the LMC catalog, and the junkyard cab I found.
Now I'm beginning to get together the parts I need.

I'm hoping to start the installation by April, since it gets pretty warm here (Phoenix) by early May.