Help hauling heavy?

[74CustomK20]

Long time viewer first time commenter over on this side of the site guys, so pardon me ignorance. I'm looking at getting an older 2 ton for hauling rock and such here soon, and am wanting some insight. I've narrowed it down to 3 older chevys, 75 c60 small block 10' bed, 4 speed 2 speed axle, runs drives dumps other is a 78 c65 unknown motor trans Or axle; but I'd assume they're the same. (maybe a tall deck? Hopefully). Third Is basically same as 2nd, but closer lol. I'll update and post back when I get more info on em, little late to bother people atm for info. What can I expect getting into the big truck game? I've had numerous square body's in the past and am not new to old chevys, but I am to big trucks. What should I look for? All 3 are dump beds, so anything specific? Is hydrolic better over PTO or electric? Help?