Attached new stainles manifolds, left hand side clamping bracket just touching chassis ( no other point of the manifold touching) right hand side manifold clamping bracket touching bottom of gearbox casing. Will this be OK?
I've seen a few car with the manifold up against the bottom corner of the gearbox, that shouldn't be an issue but as said, rattle or hum (wasn't that a U2 album?!) from the part touching the chassis could be...
What are the options? On the side where the bracket is touching I took it off and put it in he vice applied heat, put a pole inside and tried to bend slightly without success ?
Quite often you can rotate the clamp so it just misses the chassis rail.
Also you could try loosening the engine mounts and jacking under the sump - use a spreader - to move it slightly and get the few mm clearance you need.