You would need a different beam (from a Scorpio mk1 or Sierra) for the 7.5" diff as the top mount of the 7.5" diff is wider. But if you were planning on fitting a 6 degree beam anyway it would be best to get a 6 degree beam based on the 7.5" diff. I have one on the Cosworth aswell, even though I still have the 7" diff on that. I put a spacer in between to fill the gap. But at least I can upgrade to a 7.5" diff whenever I want to.