I'm brand new to this forum and am looking to purchase a 27' Airstream and saw this thread and thought I'd chime in since I have owned a V-10 2000 Excursion since new. I have towed a 24' rental trailer for a seven day trip through six states, backhoe, Bobcat and an 03' Corvette ZO6 with a featherlite open trailer.
I've replaced the muffler with a Flowmaster (it gave me a 1/2 gallon per mile boost), the Michelin heavy duty truck tires, Bilstein HD shocks, rear sway bar, steering dampener, larger transmission pan, brake modulator, slotted and cryogenically treated front rotors, better brake pads, Castrol SRF brake fluid, rear spring tightener (I forgot the name of the thing, but it raised my rear end enough where I had to adjust my headlights).
In my opinion, it is an adequate tow vehicle. It does so many other things, like hold a baseball team, 4' x 8' sheet of plywood, etc. I've got the 10,000 lb tow package and it does the job. My major complaint of the vehicle are the seats. I can't go an hour without having to stop and stretch out my back. The steering has a vague feeling about it. I tried the Redhead steering box and I must have gotten a lemon because the slack got even worse so I went back to a remanufactured one and it is back to where it was in the beginning. I've had problems with water leakage from the railings on the roof and tailgate door seal. (All fixed with clear silicone).
Bottom line: when I am too old to tow or load and unload heavy stuff, then, and only then will I sell it. It doesn't tow to perfection, but when you count all of the other benefits, this vehicle is a winner.