Thanks for the welcome.
Yes I've read that the Industrial engines were primarily detuned versions of automotive engines. I've had an email conversation with Mike Mooney (who was the Griffith factory test driver and author of "The Griffith Years") and after I sent him a photo of the engine number plate he said he remembers seeing them received with new engines, but they had no use for them and just threw them in a drawer and never used them in the build process. He wasn't aware of how to decode the various numbers. The 6001 meaning is a great start. I'll continue this thread in one of the subject forums and see what else comes up.
Thanks