WyoJim,
That is a great drive! We drove it mid-October, 2000 going from Yellowstone to Devils Tower. We didn't tow anything, but due to the blizard earlier in the week had over 1000# of sand bags plus the usual vacation stuff crammed under the tanneau cover (probably over 1500# total). I had just installed the #11 plate, EGT/Boost gauge, etc. , and had no problem pulling the hills in 5th gear. Only time we slowed down was when we got behind a 18 wheeler doing about 20 and having temp. problems. Talked to him on CB. He let us know when it was clear to pass, had no problem accelerating back up to cruise.
That is a beautiful drive, I'd reccommend it to anyone (with a CTD!!!)
Gene