Requirements to drive a beater truck off-roading (public trails)

So a couple friends and I want to buy some beater (and I mean BEATER) trucks off FB marketplace and go onto some trails. The ones I've had my eye on would TECHNICALLY pass safety inspection in accordance with the letter of the law. I have a mechanic buddy so thats not a big issue. My main question is what all do I need? I'm seeing a lot of info about ATVs but not actual cars. For context i plan on using a trailer so as not to endanger myself and others, so no highways or public streets. Basically my main confusion is what all do I need? As far as registration, inspection, and insurance, only driving offroad but on public property.

Again, I'm pretty sure this one would be public road legal, but in case it sells (doubtful) or its in worse condition than it seems.