If your going to race it put in the fiber ones. The brass will crunch with speed shifting and wearout prematurely. Been there, done that. The internals hold up fine if you don't crunch the gears. Worn blockers will wearout the other parts they mate with if you crunch them. I race mine practically every weekend and rebuild them every 2 years. 3rd gear blocker goes first followed by 2nd gear blocker. The kit has everything you need, generally except the 2 end nuts on the ends of the 2 shafts. Make sure they know it's for an SC because the truck version has one of the nuts a different size.