In the past, someone posted seeing a Northstar bolted to a 200R4 tranny which is what the Turbo Regals use. So the bolt pattern is BOC. There are at least two companies making engine to tranny adapters. The one I can think of is Transdapt. I don't know of a url. As for the using 4 of the 6 bolt holes, I wouldn't. Joe Boucher '70 RS/SS Camaro '81 TBI Suburban