Thanks, Jay. I hope you are doing well. My truck that you mention was set up as a 33GVW truck. If I had it do over again, I'd probably look for a class 8 that is set up for 53 (Tandems).
Some companies, Express-1 being one of them, will pay tractor trailer rate for any freight on the truck weighing over 13000lbs. This is a potential source of additional revenue, but there are a few things that should be considered along with just being able to haul more weight. Primarily, you'll need a place to PUT more weight on the truck.
To go along with your increased available payload I recommend a 102X102 box - and if you can swing it - a 24 foot box would be the best for this combination. I know that will require the sacrifice of some sleeper space - and the big ol' long nose trucks won't be good candidates for this kind of stretch. Cenuries and Columbias have shorter noses which leave room for ample sleeper and adequate box.
Remember - a straight truck can be no longer than 40 feet. Anything longer will be USELESS. It's not a legal vehicle.
A truck with tandems can haul more payload, will ride better (some say) but will also cost you more in tolls and tires. In all honesty, I think it is mainly just a matter of preference at this point. The added freight opportunities will make you some more money, but only if you have the rest of the truck to go with the tandems....
My opinion for what it is worth.
Thanks,
Scott