Best Used Cab Chassis for 25ft Box? 6000lbs load

Get a class 8 truck, cascadia with a 60” sleeper should give you 10 feet bbc, which you can put a 25 foot box on it, this will meet the under 40 foot requirements in all states.

it haul the weight and be dependable enough to travel where you need to go.

An Isuzu will be a tiring drive and they don’t last.

 

If you’re building a custom rv then you won’t need a cdl regardless of truck size. Get yourself a class 7 vocational truck like a Peterbilt 537 or 548 with a beefed up suspension to give you extra ground clearance.

 

Older F-450 or 550 with the 7.3 and preferably the 6 speed manual transmission are pretty stout small trucks. Most of them were regular cab vocational/utility trucks that are readily available used for pretty cheap. Probably you'd want an 84" cab/axle frame length at least. I would slightly prefer the 450 because it had the very common and not hard to fix Dana 80 rear end where as the 550 had a bigger medium duty Dana axle that was $$$ to service and repair and had a tendency for the housing tubes to crack at the spring perches from being overloaded. A big dollar repair.

 

Or a bus. Busses can be gotten cheap and would likely have a better motor that the Isuzu.