Man, nothing against 6.0 GM owners, but if I don't need the suspension, I'd almost rather pull a big trailer with my 5.3 1/2 ton. The 6.0s are tough as nails but about 10 years behind the times in power, maybe 20 since the 8.1 got tossed, but if I'm going to drop $40-50k on a new truck, I'd prioritize power and efficiency.
On one hand if I had a low mile rusted out LBZ, and the time to do it, I'd consider searching for another 06-07 Dmax with a blown engine or trans and transplant.
But you may still get decent $ for your truck if it's clean and great shape and the rust is just in the sheet metal.
Either way, going for a new truck, you said it yourself. Yesterday's best in class is today's bargain.
You could get a low mile few year old Dmax for the price of a new gasser, maybe a bit less and have your cake and eat it too.