Ok, I'm stumped

[wklink]

My GMC 1/2 ton has a 350 4bbl that runs very well but is losing a lot of oil.

I don't get any kind of smoke out of the tailpipe and the truck doesn't have any puddles under her but I lose a quart every 100 miles or so. When I get the oil changed for the first 1 thousand miles the oil stays fine but after that I start losing oil like crazy.

I haven't done a compression check but the truck runs fine, I don't feel any cylinder problems or any issues other than the loss of the oil?

Any ideas where you think it is going and what I need to do is fine. I guess i can get a rebuild done but I was hoping I wouldn't do that. The truck only has 45K on it at this time.