Wow! I never would have guessed that but now it seems so obvious. I never knew there was an adapter kit like that. Explains why there's no specific record of a change to 4" wheels and why Goodyear is on the inner ring.

I do know I've got to add master cylinders. That will be part of my field approval package. Solving this mystery was a prerequisite for me before moving forward with a 337 approval. Thanks, you made my day.