I'll save you a LOT of time. There is no unified set of rules concerning state transportation regulation. I am a member of MAASTO, an organization trying to harmonize state regulations for motor carriers. It is very difficult to achieve harmonization because some states regulations are legislated by statute and changing the rules literally means an act of congress is required.
Your question is particularly hard to answer because some state enforce differently than regulated. What this means is you could contact a state's DOT and have them tell you the actual law and what is required, then contact that states Vehicle Enforcement Division and they may tell you otherwise because they simply don't enforce this or that.
To further complicate this, you may have a trailer rated for less than the combined rating of the axles. My Stiger trailer is a perfect example. It has 7,000lb axles, but the trailer is only rated for 9,500lbs.
I would recommend contacting each states Vehicle Enforcement Division prior to traveling if you have any questions because they are the guys on the street enforcing the rules and the ones you are more likely to have to be explaining yourself to.
P.S. if you find a web link claiming to have each states regulations listed for motor carriers DO NOT TRUST IT. THEY ARE ALL WRONG! This is a fact.
