A few points... You may have 6 lug drums now. SOME 3500# axles have them.. If so, then the swap to LTs is easier.
If you are considering making the jump to LTs.. Keep in that you will likely be able to swap those tires and rims over to your next TT. I did it. The brand new tires from my new TT were a key selling point when installed on my old TT. I would rather have used Michelin XPS ribs than any no name new ST tire. This may help in the economics of the decision.
Blowouts on radial tires can shred most anything. When the steel belts start whipping around at highway speed, it is like a out of control metal saw. It makes little difference what the wheel wells are made of. Been there, done that, and bought the Tshirt.