i lived back in the day when t10's were all there was. they were clobbered left and right. a friend had a '63 dodge with a stock 413 in it. he had a t10 and t85 in it; busted both of them. IIRC, the original design parameters for them was 350ftlbs of torque in a 3500lb car. they seemed to live better in early small block corvettes (low torque and lightweight). there's a very good reason why the big 3 auto manufacturers started making there own 4spds in '64.