I have a 49 Studebaker pick up, were there doors or vent covers that came on these trucks that pass through the fender wells into the cab, I have holes in the cab but do not see where a vent cover would bolt up.
it was a couple thin sheetmetal sliding "door"s that slid along two thin metal rails that were stapled to the cardboard&fiberglass firewall liner sound deadener that attached to the firewall under the dash. sort of like an old old sliding garage door / barn door. When the old pressed cardboard firewall liner crumbled, it had most likely gotten pitched in the trash long ago. Look up the place that sells the repro cardboard truck headliners / door panel inserts for stude. It's possible they might make the firewall pads too. "Loga" or something like that? why be ordinary?
If you can't find the replacement doors and slides, you can easily make your own accurate copy if you can locate a picture somewhere. OR do what I did. Instead of putting up with a chilly cabin due to cold air leaks and too-tiny heater like most people do, I took a couple of small $5 heater cores I saw on a scrap pile, then caulked-sealed-glued them over the cabin air intakes. For the last 25+ yrs that has been THE BEST most comfy heat/cool system I have ever had in ANY vehicle. Years later I still haven't built a fan blower setup for it because it works so well. I just recently shot this pic while changing the radiator and electric fan setup. Look closely and you can see the mismatched twin heater cores. Best heat/cool vent system I have ever had. why be ordinary?