I know this won't answer the question to your satisfaction but maybe it will help a little. About three months ago I bought a '97 F150 with the same engine but 5 speed manual transmission. It had 134K miles on the odometer. I knew the clutch was shot in it when I bought it. It had been in Florida and the owner had driven it back from there pulling a U Haul trailer - I don't know how big or how much weight but I live in New Mexico and there are some fairly steep mountains between there and here. The altitude here is around 4000 ft.

I immediately had the clutch replaced and when they pulled the old one out the clutch plate was burned to a crisp and the pressure plate was blue from overheating.

As soon as I got it out of the shop I made a trip to Mexico pulling a 14 ft aluminum boat with a 35 Horse motor on it. About 1400 miles round trip with lots of mountain roads. Not much other load in the bed - probably not more than two or three hundred pounds total. It made the trip fine but it quickly became apparent to me that, while I love the truck, it hasn't anywhere near the load capacity the old '86 F150 with a four speed and a V-8 in it that I got rid of several years ago and, of course, can't begin to measure up to the '85 three quarter ton, V8 Chevy I've driven since then.

Since then I've made a couple of trips over other mountain roads with really steep grades with no load in the truck and that only served to confirm my belief.

Having said all that, I find that as long as I don't have to navigate any steep hills it does just fine with several hundred pounds of gear in the bed and pulling boat and motor. Also, virtually all of my driving in New Mexico is a altitudes of over 4000 feet which, I'm sure, cuts my power at least to some degree.