I angled milled a Hi-po drivers side manifold just a few degrees and it fit a 400 in a NARROW 65! The only reason you need to do this is to get the steering shaft to clear the manifold. In a 67 or newer I don't think this is even needed. This was after I shimmed the mounts as far over to the passenger side as I could and even slotted the steering box bolt holes about 2mm. I studded 5th manifold bolt and bent it down a little so the nut would go on flush. I would machine the steering shaft down about 2mm if I had to do it again and run solid motor mounts again. The Accurate manifold did not have the steering clearance, makes you wonder why the original had to have it.