If I thought I had to put $6K-$7K into my current truck (any brand) to make it bulletproof or whatever I'd sell it now.
What is the return on the money spent bullet proofing? Does it increase resale value? Does it give you peace of mind? Is this the last truck you will ever need?
In the end all mechanical things are subject to failure. I'll give you the benefit of the doubt that bullet proofed items may not fail . But what about the other typical wear items that are subject to failure failure?
I'd consider bullet proofing "Putting good money after bad"
Put your hard earned money toward a good truck.
If you're 6.0 PSD requires $6K in bulletproofing it is not a good truck!
Again if I need to but $6K into my Duramax just to make it reliable, I will cut my losses and buy a new truck.