Jeff and Jim : Thanks for both of your input.
Jim, while my specific case at the moment, applies to my 289 in my '67, I felt that this would be appropriate for any exhaust manifold that has an inlet tube adapter pressed in (my 1966 being my next).
As for the broken off upper tube, last summer I was able to successfully remove the remnants without enlarging the existing hole.
My subject question is specifically geared to the lower tube adapter. For similar "challenges" in the past, I have first liberally doused the "culprit" (bolt, press in fitting, drive rivet, etc.) with penetrating oil, heated the surrounding area with acetylene torch, tapped around the area, and removed with the vise grips which had been clamped around the "culprit".
I was just curious for this particular "culprit" if there was something that had been proven to be a better solution.
If not, I'll rely on the "old ways" (Falstaff).
Thanks again,
Bob