Hi Bob,
The side width is 62.6762 mm (kinda to be exact).
The 3D Repository is found down in the same section as the Buy/Sell links. The .stl is located in the Parts - Conversions, Upgrades, Unavailable and then in the folder Cowling Santa Fe.
I have the NX Model (.prt) if you want to start with that and not the .stl. I can PM it to you if you want it.