I will also wager there's a good bit of Australian Cattle Dog in his mix.
That white blaze on his forehead is a referred to as a "Bentley Mark".
This is one of my most recent pics of my dogs. The one on the right is the ACD & has a prominent Bentley Mark.
<a href="http://www.flickr.com/photos/hasfurrychildren/262503319/" title="Photo Sharing"><img src="http://static.flickr.com/122/262503319_bfab6e99bb.jpg" width="500" height="333" alt="They have their doubts" /></a>
Your dog's coat however is much shorter, but has the spotty markings that are brought to the breed from the mix with dalmation.
Whatever is in his mix, I say who cares! Same as my dog on the left.
CONGRATULATIONS!!!! Thank you for adopting.
He's a gorgeous dog & I bet you're in love already. :)
PS. Best link I know of about Cattle Dogs:
http://www.cattledog.com/misc/history.html