904 tranny recipebehind 360
^^ I agree...
And If you have access to a 998/999 rob the output shaft and thrust washers that come on the front of them. Those shaft have a much better design oil feed hole out the front than the older shafts. They oil the thrust washer that's between the rear clutch drum and output shaft much better. They sling oil out sideways to keep that thrust washer protected under high hp use. Seen the older 904's output shafts eat up that thrust washer if you put a bunch of hp to them. If not drag racing? Older shaft will live on the street.
And if you want 5 clutches in your high gear drum? Easiest way is to buy the thinner clutches.
You can use the 5 clutch drums from the 998/999's but you also must have the correct rear drum that has longer splines that will work correctly with those 5 clutch drums. And the back side of the pump is also machined differently to clear the offset of those 5 clutch drums. Easier to buy the 5 of the thinner clutches and set up them up in your 4 clutch drum.