The brakes and suspension are simply not designed for the task.
Adding 6BT will help get the load moving along but will exaggerate the issue by adding substantially more weight.
The thing that you need to understand is if an accident occurs no matter what it’s your fault as you shouldn’t be on the road in the laws eyes because you’re overweight this is the liability I speak of.
It’s your truck do what you want with it
If you want the noise and vibration of a concrete truck go ahead and do the 6BT swap

There’s a reason why they almost always get sold shortly after the swap is complete.
There’s much better swap options IMO
Have a great weekend