I replaced my 302 with a 351W. The header bolt patterns on the 302 & the 351W were the same. My issue was that the deck height was taller on the 351. This means the 351 headers set higher and a little wider in the body. I replaced my engine mounts and brackets with modified ones that lowered the engine about 1/2". These were supplied by the manufacture of my Cobra (Classic Roadsters). The only issue with that is now my
oil pan sets lower than my front crossmember.
Terry