Thanks Jim...the illustration you posted is definitely for the 6-Cylinder application and is the one I would prefer to find; all of your dimensions are correct as well. You're just the kind of person you hope to find in a forum like this; helpful and willing to spend some time finding this kind of information to post.
I've posted a far better photo of the 8-Cylinder Tee, it is rounded and I would be happy to find one of these as well. I will have to modify the 3/8 male thread; not too difficult, as long as the inverted flare female threads and seats are in good condition.
Thank you all.
Ray