Thanks for the great responses so far. What is the next way the trannywill shows signs of its age? Currently there is no slipping out of gears, and it shifts all gears. However, the are various vibrations. I'm going to replace the center support mount and bearing and see if that helps. All of these vibrations are felt in the gas pedal, steering at speeds > 60MPH. At 77 the car has a different feel and has thru several sets of tires and other suspension work (to fix other problems) so I pretty sure its either the tranny or driveshaft. It seems shifting out 'D' into '3' makes the ride smoother at mosts speeds (not as effective at 77) which makes me think its tranny related.
I have another tranny and TC in a car with 175Kmi (part car, hasn't been run in 2 yrs, tranny known to work well). Is it worth pulling this tranny or is likely past its time as well? What about the TC? Mix and match?