His name is Pat Brady <bbunch@ameritech.net>, if this is the same guy I've corresponded with. I checked with him before I bought my 4x5 enlarger in April to be sure it would accept the head, since I'd like to get one further down the road. I'll paraphrase his reply.

He told me it fits any enlarger that fits the Beseler adapter for cold light heads, such as Calumet's stock number AI1005.