Having 6 clutches in a 904 is the most desirable setup but 5 will obviously hold better than 4.
Just out of curiosity, what is the PK number on the pan rail of your unit? For reference, I've attached a PDF of the trans guide that's been on the internet forever. It lists unit PK numbers from 1965-1986.
If anyone cares - almost exactly ten years ago I detailed the assembly of the 904 that's in my Duster.
Click this link and go to post 182.