Hi Mike
Checked my list of built sheets and it seems that I don't have a sample from another car matching your car's description so, it will take a few more steps but lets see where this leads. Basically backwards engineering for the info
What are the numbers on you leaf springs - the short leaf?
Also - is there any color left or just a section where the surface texture is different?
IF there is any color left you can spray some over cleaner over the area and when the chemicals react they will expand and highlight the color for a few seconds allowing you get an idea of that was there.
Left see if we can get you some answers