Well as a "retired" truck driver you need to slow down early and use engine braking when stopping heavy loads.

Now as a FedEx driver who eats brakes for lunch...stop using ceramic pads, they are to hard and will eat up your rotors.
On my E-250 I used NAPA Severe Duty brake pads, replaced them every 4-6 (both axles)weeks and did rotors once a year or so.
On my Sprinter, same pads, again every 4-6 (both axles)weeks and rotors every 6-8 months.
Stop using ceramic pads.

 

I doubt the 450 parts are interchangable. Someone else might correct me. But yeah a 350 is a light duty truck and 450-650 are considered a medium duty truck. Unless you want to swap axles i dont think brakes will work. But definatly lose ceramic pads get some regular or heavy duty brakes. As far as loosing a pallet if you were in the north east we might be able to arange something lol

 

You could also get an exhaust brake put on too. Kinda like a "jake brake" in a big rig. My old mans delivery truck has one definatly helps