The Mystery of the Right Side Spare Tire on my 1930 PU?

[1930-Pickup]

The spare tire on my late 1930 pickup is mounted on the right side.

Maybe your first thought was like my first thought; Ford's manufacturing practice was to mount the spare on the left side, so this truck has been modified at some time in the past. Statistically speaking, that's probably a reasonable assumption.

But not so fast my friends...
- This mostly original truck has never had the body off the chassis.
- The left side of the frame was never drilled for a spare mounting bracket.
- The left side splash apron does not have a mounting bracket hole.
- The right side spare mounting bracket has the same patina as the frame.
- The rear axle is 4.11, and it has a 10 leaf spring.

Features indicate the pickup was probably built between September 1930 and April 1931. The frame number is buried under the cab, so its unreadable. The engine number indicates April 1930. The title VIN is using the engine number, and I know the previous owner 'fudged' things.

I think its reasonable to say that this pickup body came from the factory with this frame. But why does it have a right side spare tire, contrary to Fords standard manufacturing practice for the pickups?

It's common knowledge that Ford used 'extra/left-over' parts for the commercial line...is the unusual spare mounting related to that? Or, could it be that the pickups were so much less expensive than the Fordor sedans during a time of the deepening Depression, and Ford had too many sedan chassis already built up?

I would really appreciate your thoughts on this mystery.