differnce between 1966 904 trans and 1967

The hole in the crank is larger after 68 than for pre-68. As was mentioned, you can get an adapter bushing from Torqueflite Patty to use the earlier torqueconverter or swap out the front three main components in you pre-68 tranny with the 68/later so you have the more modern input shaft. Then there is a large selection of torque converters and all you need is a balanced one or the B&M flexplate with balance.