That is why I made my M51A2 (now doubling as M52A2) fully
road legal in the Netherlands as opposed to messing around under Czech veteran papers. The question is not what I can get away with or what is possible, but what is legal and covered by insurance.
The pintle is not accepted in Europe for ANY vehicle except military. All civil have to have automated fish-mouth couplings.
When I came with my truck to the DoT, the asked for the company specifications of the original pintle and of the frame. I told them the company did not exist anymore and showed them the original documentation (dash tags and TMs). The Dutch DoT then had a good look at the frame and at the motor specification, and on that based my max allowances. In this case, they said that the motor power (max torque and HP) were more limiting than either the old pintle, the frame dimensions, or the new fish-mouth. For my truck, the final conclusion was that with the new civic coupling, I can pull 69 000 lbs with an M51A2 (provided the gross train weight does not go over 90 000 LBS)
I have that black on white as a Europe-wide certificate stating.
Don't worry, I will never do that but the point is, legally and according the insurance I can do so if I want.
As others said, if you want to do it, do it good. Get a statement from a company certified by the DoT or by the DoT itself re-certifying the max towing load under normal road conditions. Under no condition, go over what you have on your papers; the fines and liability will definitely not only top the re-certifying costs, but possibly the entire worth of the truck.
CMS Davis, impressive! Probably a wee bit over the max height as well. This was on a public road?