I'm using the Schumachers on a 6cyl K-Frame as well.
How can you shim the mount? You mean go up with the engine by throwing a washer under the motor mount (can you do that? does that weaken the mount?)? I can't do this anyway because the header tubes that wrap around the driver's side frame rail will also go up and hit the frame. Thus no room to go up with the engine.
I guess my only recourse would be to keep on cutting or call ProParts to see if my header bend is messed up. (if they even exist anymore).
