I didn't think that spotted draft was a breed, I thought the registration was just to preserve a rare color in draft breeds but I'm not an expert haha. So I searched it on google and found the NASDHA website North American Spotted Draft Horse Association
or maybe this site will help? http://www.pinto-draft-registry.com/members.html
I would check those out and see if there's any info there.
Sorry if that doesn't help!