Bob,
Pretty sure my dog is an Aus Shepard/Lab mix. Great mix IMHO. Fun, protective, smart (unless compared to a border collie), nimble and hardy. I have a female that runs about 40 pounds. She's now 9 and except some grey in the facial hairs, looks like a 2-year-old. She has short hair like a lab but you can still see every muscle in her body (looks very athletic). At 2-3 years old, she could run 25MPH. At 9-years, she can still do 22MPH. Except for getting Lyme's, vet bills have been incredibly low.
Guess I'm saying that if an Aus Shepard (or mix) is an option, they may be worth giving a close look.