The 7.3 was made for WORK, and LONGEVITY. Keep up with the maintenance, get gauges, and simple mods like the ported housing, ww gen one or two, exhaust, quality programming blah blah blah, and you will be just fine. Learn from the awesome "jedi" on this site like I did!
Ive been been pulling loads like this for years with no major problems. I live in hawaii, im either going UP a mountain or DOWN a mountain, and my truck earns its keep. Sure a 6.0 or a scorpion might pass me on the fly, but in ten years lets see if there still working like the day they drove um off the lot!!!!
By the way i took this load from kawaihae to kamuela town. It goes from sea level to 3000' in 11 miles. Never slowed more than 35 mph. trailer= 7k, mini-x 7k, skid loader 10k, not to shabby. LOL BTW i do ths all the time, so dont worry your truck can handle, dont be scared to make it work!