Are you thinking of the SOHC conversions from Pete Aardema?; http://www.aardemasohc.net/index_files/Page313.htm
If you go to his home page he's developing some Infiniti head conversions, but doesn't sound like they're ready yet.

The Moser DOHC setups that HRP put up are the only DOHC one's I remember, and they haven't been around for more than 30 years.