999 clutch pack in a 904' & opinions on fluid

I've read where people say to put 5 discs in the forward clutch as opposed to the 4 that I have now, but never see part numbers and details. I've recently read that the A999 trans is the 5 disc version of the 904. Do I simply order clutch parts for the 999?
Are the 5 frictions and steels thinner, or are there different pressure plates as well? Any actual part numbers? What else will be needed to make this work?

2nd subject; fluid. Having a Chrysler Torqueflite, I would be inclined to use ATF+4 fluid. Somewhere I read that aftermarket frictions (Alto Red Eagle)are designed with Dexron in mind. I have a L\U Torque Converter made for a Chrysler. Will Dexron fluid cause converter shudder, and\or will ATF+4 cause clutch problems?