80 ft lb to turn an engine with the plugs removed seems high to me, but I cannot say I ever measured it. I know my 347 (5.0 stroked) takes considerable effort to turn with the plugs out. You are turning the
oil pump, which will pump
oil. You are turning the belts and water pump, which will take some effort. And, you are turning the transmission too.
You may want to have someone push the clutch in and see if that reduces the friction. If the pilot bearing and transmission are not aligned properly, that would add friction.