Here in Wyoming horses are the way to go for hunting. There are several breeds that are good. Ditto on what was said about mustangs. I had a little mare that was caught wild on the desert here in WY. She stood maybe 14 hands tall and weighed about 850. She would carry me in the mountains all day long and not stop until I stopped her. She had the sharpest sense of any horse I have ever seen.

Quarter Horse are pretty popular for hunting. Same with Quarter crosses. From what I have seen Arabs are hot. Take each one individually. Same way with TB's. Draft and draft crosses are good. Haven't used mules but I haven't heard anything bad about them in the hills. You might want to take your percheron mare and breed her to a mammoth jack. This is a really good combination. Crossing her with a TB would give you a good colt too. Tennessee Walkers are well respected in the mountains. I would like to try one crossed with a Quarter Horse.

Ann from Aspen Hill Adventures (she posts on this site and AR) did have a Belgian/TB gelding for sale. It might be worth you while to contact her.

One important thing I look for in a mountain horse is a good strong chest. You get one with a narrow chisel chest and they will have trouble going up hill & down. I would recommend a gelding. Mare can get tempremental. Studs can be dangerous.

Here are a couple of web sites where you can go and search for horses.

http://agdirect.com/scripts/main.exe?2053

http://www.equine.com/horses/search.asp?ignore=1001