I bought one of those, exactly like yours, new in 03 to pull my 6400 pound empty TT. Add a shell and two big dogs all the gear and we have about 8000 I figure. First trip was to Yellowstone then Colorado. I thought I was going to blow it up on some of the grades. When I got home the dealer was going to "unwind the deal" till he saw the miles on it. I sold it to my son who still has it, no problems. I bought the same truck again with the diesel, problem solved. The only advice I have for you is go back to stock E rated 265 tires, that will help big time, and keep them aired up.. Then slow down going up the hills, you can make up for it going down, lol. Mine didn't like the hills either. My trip had me go over the devide more times than I can count, 11,000 feet at times. Try to keep the TT as light as you can. Don't re gear. Don't add a bunch of aftermarket stuff. That hemi is putting out as much as you're going to get out of it without going nuts with it. Besides, I think the problem lies in the trans more than the hemi. Use premium gas when you tow, it might help a little. keep it serviced, syn oil, the best filters and plugs. It will go a long time, just not fast up the hills. BTW, the same hills I struggled with the hemi at 45 I go right up at 55+ with the diesel, and it's only the 235HP SO diesel.
