I have been researching the wheel finish on the Shelby GT40 MkII's that raced at LeMans in 1996 in period photos, so I could repaint my GMP Miles/Hulme cars wheels. From what I have learned, the Halibrand magnesium wheels sourced by Shelby American were left unfinished, and actually looked a bit scruffy. Different sets of wheels used during the race looked different. The gold color was actually due to a liquid that was applied to the wheels to check for leaks through the porous magnesium. It was more pronounced on some wheels than on others.
In my opinion, the wheel finish on the Exoto and GMP GT40's is too refined, and not really historically accurate.

Don Klema