Correct me if I'm misunderstanding you but are you saying your using a flexplate made for a 727? If so, your probably also using a 727 converter, correct? 727 converters are larger diameter than a 904 converter and have 8 more teeth on the ring gear. If you are trying to use a 727 flexplate and converter from a 727 in a 904 case it won't work because the larger ring gear puts the teeth farther out from where they should be.
