Are you sure the JY one isn't a model "999". I have read about it. Almost same as 904 but w/ 5 disk clutch and lower 1st gear. It is rare and desirable. I understand it mates up fine, but some issues with the wiring for lock-up TC, etc. Does it have extra connectors? If you rebuild your 66 trans, I have read about swapping the input shaft to use a later TC.
