The sizes for the spacers/shims will vary from car to car.
Ians guide in the Articles section shows what needs doing, but you will need to make your own measurements to make sure of a good fit.
A good metal fab shop will make the spacers up for you, for a few beer tokens
As for the 6 branch - I think there are problems with fitting any of the available M20 6 branch manifolds with the E36 rack. The steering joint is moved closer to the engine by about an inch, so it hits the manifold.
A custom manifold can be made to fit around it. I had to re-plan the route of my 6 branch with the E36 rack fitted.