Engine leans right and Passenger Header hangs low - Why are engine mounts different?
 

Why is the passenger side engine mount shorter than the driver side mount?
I have a 69 Lemans convertible with a 1974 455. The passenger side header is at least an inch lower than the driver side. The engine has a noticeable tilt to the passenger side. The headers are of unknown brand, they came with the car when I bought it. They could be part of the problem, but the engine tilt is noticeable. See photos.

IIRC, the passenger side motor mount on the frame side has some adjustment built in by way of the holes in the frame being elongated from the factory. I would check that first followed by the mounts bolted to the engine block as they may be worn or low quality replacements. The headers should not be a factor in how the engine sits on the mounts.

I resolved most of this issue by installing a new passenger side motor mount and by adding a shim under the frame side bracket, also on the passenger side. The engine tilt decreased from 2.5 deg to about 0.5 deg. The passenger side header is now only about 1/4" lower than the driver side. The old motor mount appeared to be slightly bent and slightly shorter (compared to the new one).

looks good! I had no idea that shims existed for the frame side mount so that is good to know.