Cracked Flex Plate

The flex plate only transfers rotational energy, the crank supports the convertor via the snout into the crank register.

The later cranks (post 67) used a larger crank pilot bore that the later convertors snout nested in snugly. Same as the pre 68 cranks: Smaller crank bore and smaller convertor snout. If you put a early trans onto a later motor, your snout will be swimming in the larger crank bore and it will not naturally center. Like a Mopar rim, it needs a center register, 'hubcentric'. It will eventually run out and put stresses on the flexplate ears that will crack them. The bushing is 1/8 walled to fit the early convertors onto the later cranks. 'Tflite Paddy' sells them as well as others.