Just last week, I replaced the passenger side engine mount on a 1974 455 in a 1969 Lemans. I also added a 3/16" thick shim matching the frame side bracket. Before the engine was tilted 2.5 degrees to the passenger side and the long tube header was much closer to the ground. Afterwards the engine was at a 0.5 degree tilt and I gained about 3/4" ground clearance on the passenger side header. Car was up pretty high on wheel cribs in the front and jack stands under the back. And I couldn't use my engine hoist due to the car's positioning in the garage. So I very carefully used a floor jack and a block of wood on that side of the engine. It was tight but it worked. See pictures in other thread. Purchased engine mount and shim from AMES.
https://forums.maxperformanceinc.com...d.php?t=884158