You got it. Thank Scott and DVW for doing that though. The post has been archived for a long time now since it's almost 20 years old. It's still the only thorough reference out there for modifying 904s though so I'm glad it's still viewable. Just be aware that some of the part #s that got added in towards the end may no longer be available or have been superseded.
Several years ago I made a post of my own on FABO specifically about the 999 variants. To be clear, my post was only to show what the few application-specific parts inside look like.
How to identify a 999 transmision.
Though I wasn't old enough to know, I have a feeling back in the '60s and '70s no one gave a rat's *** about 904s. There's a brief passage about them in the old Mopar Chassis bible so the factory engineers must have understood their benefits in milder race cars but I'd bet most of the time they got pulled and scrapped in favor of a 727.