TrailBeast
AKA Mopars4us on Youtube
I installed 5 discs in a 4 clutch drum in my 904. I had the pressure plate machined with a narrow groove so the snap ring could be installed with the proper clearance.
Aaaand there it is.
I have done this on a bunch of different transmissions, and it works perfect.
Won't work for that drum obviously.
There isn't anywhere near enough room there for the extra clutch and steel and then the lock ring.