Overall length is all you have to worry about,as far as I know,I'm not sure what the legal length is...75' sounds right.
As long as you are not doing it commercialy then you don't need a CDL,or any endorsments.(that's a fact here in Idaho,not my opionion)
Make sure that the pinbox is good for the combined weight.
I think you might need a "T" plate (T for truck,not commercial) ask em' at the dmv,you can get a regular plate up to 26k I belive.

 

Yep, Thats what I have found out, during my investigations , Thanks for the confirmation.

 

I pulled doubles with a semi in the school parking lot, pulls real cool, you think it's going to cut short a corner but it doesn't. I haven't put the endorsement on my license though, might if I get a driving job someday, when I get tired of working inside.