the hole for the beam should be closest to the front of the car.
having my own arb based nightmare at the moment, found that the morons that did some mot work for me refitted them in opposing orientations
one with hole to the front the other to the rear. this was causing exactly the sort of manifold rubbing you are talking about...
decided to try and sort it myself rather than deal with those idiots again, tho now having trouble getting things to line back up right.