Mel Pinto imports was a longtime importer for the ALAN 303 frame, which is what this is. And, they were still being made and imported by Mel Pinto as late as 2003. So your best bet is to get a recommendation from Mel Pinto himself as to who could repair the frame. Mel has been a fixture in the cycling industry since the 1970's at least.
http://www.melpintoimports.com
While you're on the website, I think he might have one or two ALAN frames available WITHOUT the cracks in the head lug.
http://www.melpintoimports.com/
The other choice is to search for "alan frame and repair" on www bikelist.org. There is at least one other builder who could tell you the chances for a successful repair.
http://search.bikelist.org/
the main link, http://www.hhracinggroup.com
- Don Gillies
San Diego, CA, USA