In SC, whether you need a CDL or not is determined by the manufacturers rating. You can tag an f150 for 80k if you want to give them the money.
There are 3 ways to get a weight ticket in a vocational truck, (one of those listed as exempt from federal bridge law).
Being over your tagged weight. $200
Being over 20,000 lbs on any one axle. $small fine
Being over the gross allowed by your number of axles $$$big fine
SCDOT doesn't care what you do with a pickup and trailer, basicly. One of my best friends had an employee driving an F250, pulling a dual tandem gooseneck, with 20,500 lbs of material on it, so a about 26,000 lbs of trailer and load. When he got to a construction zone, the flagger stopped the car in front of him. He clipped the back bumper of the car with the trailer, and centered the F250's grill on the flagger, killing him.
At my friends request, I observed and assisted the DOT and insurance investigators on seperate days in going over the truck and trailer with a fine tooth comb. They found the equipment to be in good shape, except that 2 of the electric trailer brakes were not connected, and one was badly out of adjustment!
The driver got a warning for having no medical card or CDL, and a $160 ticket for too fast for conditions.
The Owner got a long list of warnings for basic equipment and paperwork, a $200 ticket for having no license tag on the trailer.
I have never seen SCDOT do a roadside inspection on anything smaller than an F600, and very rarely on anything smaller than a tandem, though tandems and up can plan on being stopped once every couple of months. I have never heard of SC giving a ticket to anyone for not having a CDL for pulling over 10,000 with a pickup, though NC burns them up. I once had to take my drivers to NC to rescue 5 of my cousins F550s pulling big welder trailers, NC wouldn't let them move without class A drivers.