The thing about towing, every truck is rated by the manufacture for what it can safely tow. Sure you can beef it up, brakes, axles etc. but you still need to get it re-registered for the new specs. In Pennsylvania this would involve a safety inspector to sign off on it.
If you did not change the registration, and were in an accident, it would be your fault no manner what. A lawyer could prove you should not have even been on the road towing more that the truck was designed to tow.
I know every state has different rules, but every state has lawyers.
The other issue here in PA, unless you know the inspector, and he/she knows you, it will be hard to re-register a 34 year old truck for more capacity.