Or so says the owners manual.

All my truck has is a thin piece of waffle like pressed fiber glued to the underside of the roof, Did the mice make off with the rest of the insulation, or was that considered "well insulated"?

That was considered being well insulated.

In 1949-1950 and early 1951 the Deluxe model cars a a rubber foam type of padding above the head lining. In mid 1951 it was changed to a rubberized straw..,,You could tell it soaked up noise because the Deluxe models were quieter than the lower priced Specials.

Thanks for the info. I have gotten pretty used to the "airplane" sound.

(Not sure why I posted it in this forum, sorry )

Most of your noise, heat, cold and stink is coming through the firewall. Then the cab is small and there is no "cloth" to absorb the noise. Place some carpeting over the floor mat or a blanket on the seat and the noise will be reduced by 50%

Will try that suggestion, thanks.

When I first got my truck, mice were living in the doors and above the head liner, and it smelled horrific. I stripped out the headliner and the metal panels and hosed everything out and then sprayed everything down with Lysol. The weather-stripping came off with the panels and the mice removed most of the insulation and it did not come with a floor mat. I'm sure that contributes to the deafening roar at 60 mph.

By the way, did these trucks have a jute pad under the floormat or not? I'm a little worried one would absorb moisture and rust the floor.

Yes, they had the jute pad cemented to the underside of the floor mat. I would just check for time to time to see if its wet.
Replacing the big truck fan blade, which is unnecessary for normal driving, with a fan from a car would also help

I'm not so worried about the noise that I have to do something as drastic as changing out parts. More just curious if they were that noisy when new. However, I did install a floormat and pad in my truck today and just that makes a significant difference.

Back in 1941 a truck was a truck and the noise was considered normal.