I think it is a bit more complex than that. The light is a 24-28 volt. Unless your truck happens to be a big rig, it is not likely you have 24V electrical system. From the details we can pretty well estimate the power requirements.
If it runs on a pair of automotive storage batteries for an hour, that says it needs about a kilowat. Most automotive storage batteries are in the 50-85 ah capacity range, so 1 hour is 1.2 to 2.0Kilowatts. The option is for a 1.5 kw generator, so this estimates passes the 'sniff test'.
Many newer vehicles today have 100-120 amp 12 volt systems,
and that is going to be barely adequate. I^2 x R losses in the wiring become problematic at those sorts of currents, and the vehicle itself has so many electric bits and pieces that with the headlights on, you probably need 60 amps just to stay even.
.01 ohm in the wiring at 100 amps is 100 watts in heat! (hence the 4 gauge copper the auction talks about!)... So for continous operation, you are probably going to need to install a separate 24V alternator/electrical system, although the 1.5 kw generator unit may be an easier choice. If you want a 24V system, These can come off a big truck, or a light aircraft-medium aircraft.
(Aircraft with 520 and 550 cubic inch engines and up have 24 volt electrical systems, that start with a 60 amp alternator and go up from there).