Do you have a Factory Assembly Manual? If not it's a valuable resource that you should have. It's available on Amazon and other places.
There's a diagram of the side mount spare carrier. Section 10, Sheet 3.00 and 3.01 cover the side mount spare. It has some dimensions.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.