Heated trailers have those holes, too. The tank is mounted a little bit farther in so the skirt can work properly.
The other aerodynamic feature I see on trailers is a big plastic spoiler-looking thing underneath in front of the wheels.
Side skirts on van trailers have become so common now that to not have them would be a special order. Combined with the tails gives an improvement in fuel economy when deployed. My company only has the skirts, though.
Eaton Fuller transmissions have been the standard for years and wouldn't have changed much externally since that kit was made. They're not synchronized and popular variations are 7, 9, 10, 13, 15, and 18 forward gears.
If you ever wanted to know about the commonalities between the various Revell pro/street kits, here you go!
https://sprue.xyz/2020/06/07/dobbertin-pro-street-chassis/
Any 1950 Chevy pickup with four wheel drive from the '50s would be an upfitter like NAPCO or Marmon-Herrington. Those components might look different than what you'd find in any kit. Swapping the body onto a newer 4x4 chassis is fairly common and the Deserter chassis is the easiest one available.
That was indeed a typo and has been fixed. Thanks for catching that.
Whoa, that is interesting! It is listed as 1:25 scale, suggesting that it isn't related to this chassis. It does look like a rebox of the Pennzoil Firebird with smoked windows, though. If only there was a number on that box!