I have often looked at the PTO option on some of the 1994+ 2500/3500 Dodge Ram trucks and thought something like:

“If I had one of those PTO’s hooked to a 3 phase 120/240 generator,
I would not only have a portable electrical generator station,
I would also have a “DYNO” to test the engine fuel economy at various % throttle and rpms.
Just generate and measure the electrical power fed to a resistance heater.
I could predict ahead of time what MPG could be got with various gear ratios, because I can calculate aerodynamic and tire rolling resistance power.

Reading this post I can now add:
You could add more air conditioning options for the truck cab too.
Use the PTO/generator to supply power
to one of the “portable room air conditioners” with a single hot air outlet house.
(drain the condensate water through the floor of the truck cab.)

Another factor to consider:
if the portable air conditioner developed a fault,
quickly swap it out as a module.

Wouldn’t it be interesting if each “system” in a truck/car
was a “quick swap module” if it was not too expensive?

The Hubble Space Telescope is a collection of modules
( except for the faulty Perkins-Elmer built main reflecting mirror,
which should have been instead the correctly polished Corning Glass Company mirror, which NASA bought, paid for, and put in a warehouse... no kidding)