Well I took the time to mock up the parts and take a close look at where the frame bracket and the header tube where trying to occupy the same space. I marked the bracket and removed it a few times and tried spacers here and there, but I think that it would be best to modify the frame bracket and not use shims. The shims seemed to create alignement issues with the motor mount and frame and possibly put the passenger side is a bind.
In the pictures below, the offending area is the chipped paint inside the black "circle" the chipped area is right where the tube hits the mount. It looks like I can cut down that "high" spot and leave the flange below it. In the second picture, imagine that the socket is a hole saw, I could clamp the bracket in the drill press or mill and run the hole saw through the area at an angle that would be parrallel with the line the header tube follows. This would take out the area marked by the black "circle". The slug could then be flipped over and welded in from the bottom therefore maintaining the strength of the mount. What do you guys think of that solution versus the one described above? Both require fab work which does not bother me at all, but I just don't know which will look better in the end.