It is good to see you are doing the rebuild yourself. It's not that difficult and you'll know what you have when you're done.

Since you're in there I'd go for 5. I've had good luck with Alto Red fibers and Kolene steels. Like jbw123 noted - you can get different thickness fibers and steels to make room.

I'd also check all tolerances since you didn't originally set this one up. Set everything on the tighter end of the specs.

I'd purchase Carl Munroe's book: https://www.amazon.com/Torqueflite-727-Transmission-Handbook-HP1399/dp/1557883998. There's still lot's relevant information in there.

If you're interested, I'll send you my 904 build notes for reference.