On my Freightliner Cascadia it has a separate tank between the battery box and the fuel tank in the driver's side. Most fueling stations have bulk DEF/AdBlue pumps built in to the diesel pumps. The pricing is around the same per unit as the diesel these days.
I don't know of any kits that come with a DEF tank, however I know KFS offers them.
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/