If its an older car, replace the pinion shaft with a new one. The alloy shaft can ware under the bearings (it will be marked if it has) and allows too much movement and thus causing a problem.
Build as pr manual but if racing on mega high grip carpet, then take the copper shim from one side and put it on the other as to make the shimming cap 0.2 tighter (the shim is 0.1)
The other thing to look out for if its an older car is the top gerbox casing compared to the lower gearbox casing. For the small price they cost and for the peace of mind, I would replace the casings too!
Hope that has helped a little......