It's actually a billet clutchpack drum that you need (The part that explodes when the sprag lets go)
If you are referring to a spring retainer, then I don't see that as a necessary part.
The sprag, or one way clutch in the rear of the trans and the billet front drum are the important ones to help keep it from exploding.
The amount of springs in the drum can vary just from personal oppinion, but 12 is what we used to use.
Now with a manual valve body that could need to be different, and I don't know that answer. Sorry
