Okay great. Thank you. I'll check under the truck for the cab mounts tomorrow. What's the diagnosis if there are two cab mounts in the center?
I've noticed driver side vent doors on the 47-49's have a knob. This truck's is flat. Distinct of the 50 trucks, right?
Here's my theory. This S/N date backs to April 1950. Still early in the year. There were some '49 cabs left. Chevy used the 49 cab for my truck, because the average consumer wouldn't know any better. But they HAD to change the vent door knob to the '50 design because leaving the knob would be too obvious of a 'dated' car. So they switched the vent door.

Plausible?