Rand suggests the Cross-Domain Rel Canonical in his WBF vid last May: http://www.seomoz.org/blog/cross-domain-canonical-the-new-301-whiteboard-friday. Go to 4:00 into the vid and I think that is more relevant to your situation. I think the other questions are: Are these old pages ranking well for particular keywords? Do any of these pages still get recent traffic? Do any of these pages have any strong links to them? Those are the ones you want to bring with you. 
