Thanks for all the info!! I'm looking at trucks AND SUV's (found a Chevy Avalanche for sale I'm interesting in now...4X4 with 5.7L V8 engine, 7,900 lb towing capacity)
The Durangos I'm looking at are all V8's and 4X4 (whether I end up with a truck or SUV, I want a 4X4 option). And yes MyBoyPuck it's the 4.7L. Although I think it's only rated for 6,500 lbs which is cutting it a little close (reason for this thread, I'm a little on the fence!)
The horse trailer I'm looking at is about 3,000 lbs empty -- add to that another 1,000 lbs of my horse and avg. 1,400 of someone else's and you have the tow weight now up to 5,400 which is at 83% capacity - that 75% rule mentioned above it a pretty cool rule of thumb by the way!
So I don't know, the more that I think about it, the more I'm leaning towards a nice Dodge Ram or that Avalanche! ;)