Shims would work.......
Redfish, if your motor mount is like mine then the two ear'd side of the mount is the front of the motor.....if that is correct then that actually worked for me. It does not fit easily when there. Also, a local guy here has a 340 matching number 69 and his mounts are to the back of the ears (not what you are showing or what seems to work) on his car.....he has original manifolds, perhaps more tolerance with the manifolds.....
I will try moving my motor mounts again....
If anyone has a picture of a 340 driver side motor mount that would be great.....top view, side view.........