Thanks Larry, those are the drawings and photos I had. I had roughed out a spacer, and laid it out on the tub accourding to the drawings, but it wasn't hitting the tire and wasn't thick enough. Looks like I need to move it up the fenderwell a little bit and make the spacer about 1/8" thicker. I'm using a reproduction spare tire carrier on a reproduction tub so it may stick out a little more than the factory one and be in a slightly different location.
I'm assuming it should hit in the "fat" part of the tire?