Have a '77' 450SE 4.5 , I replaced starter last year because it would occasionally not engage (screech) and it had started fine since. I am now having the same problem (not engaging w./ screeching noise) and yesterday had to turn engine by means of wrench on pulley in order to start. What would be the best way to check if the ring gear is faulty? Any help greatly appreciated.

You may be able to remove the cover on the intermediate flange and get a look at the teeth on the ring gear. This is the cover that you have to remove in order to get to the bolts that holds the flywheel to the torque converter. Good luck. Bill Lewallen.