as title says.... have a question on dash pad.... do the factory "heat only" trucks have the place for teh AC vents "marked out" on the back sides where a guy could cut them out later and add them in if needed or am I gonna have to get a different dash for this thing?
I did get a plenum box out of an AC truck along with all the associated ductwork. The guy had already sold the dash itself and the control head so I still need a few things for the inside of the truck. just need to find out if a different dash itself is among what I still need or not.
Either way Id need the louvered vents that go within teh dash and a inst cluster bezel out of an AC equipped truck.

also does anyone sell replacement pre cut foam kits for these trucks, for the various plenum doors and such?

detroit muscle sells the foam kit but it does not include foam for the mode doors. the doors are not avail any more, so i went to the upholstery shop and got thin foam from there. cleaned doors and used headliner spray on doors them wrapped foam on them. 1 door has an extra large piece of foam on it for a stop. i just reused the thick part. kit is pricey but well worth it, imho.

For proper opperation you need a A/C dash. Or you need to do some custom vents. If not it will just blow teh cold air under the dash.

I gotta take the dash out to swap out the plenum anyway, was hoping for some kind of marking on the backside where I could cut out the vents to fit in. The VIN is with the dash on these, and my dash is in real good shape so I wanted to retain it in the conversion if it would be possible

You don't have to remove the dash to get the box in or out. The dash is not marked for the vents but when we added A/C to those trucks at the dealership we had templates on where to cut the dash for the vents. Those vents pop in and out. Just drilled the four corners then used a soldering gun with a flat blade tip to cut the dash.