Intense Racing and ZZP both sell upgraded input shafts which is the first weak link to break. The next problem area is the chain set and many places including myself sell an upgraded kit that converts it from a dual chain to a single chain arrangement and handles quite a bit more power. ZZP also offers a stronger output shaft and oil pump shaft which I really havent found a need for the pump shafts but they are a nice part and eliminate concern for spline wear as they are much stronger. Really an input shaft and chain will get the trans deep into the 11s, and a good build on top of that of course to assure the clutches live
