I know in Florida I weld 2x3 box tubing between the framerails at the rear of the frame so its behind the rollpan and its legal that way.Just having a rollpan wont pass here.The rear framerails have to be connected.I always take my trucks to the local state troopers office so they can check it out,and get them to write me up something to keep in my glovebox so I dont have to worry about get a ticket for no rear bumper.
In the 80's and 90's you could by a new truck without a rear bumper,BUT you had to sign a waiver that said you would install a rear bumper within 30 days.So yes you could buy a new truck with no rear bumper,but by law you only had 30 to put one on or it was illegal.