One thing I would do is narrow down the tire search by tire size. Specifically, what diameter tire makes the speedo read correctly?

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Also got an education at Sam's. Seems they will only install the exact size listed on the door jamb sticker, which in my case is 235/65/16.





That is approximately 28.0" diameter tire.

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However, I have the original window sticker for the truck. It says:

Standard Equipment (Unless replaced by optional equipment)
Tires-P235/70R15 XL OWL All-Season





Also just a smidgen less than 28.0" diameter.

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However, under Optional Equipment is the Customer Preferred Package 26C, which includes P265/70R16 OWL All-Terrain, which my truck came with.




Approximately 30.6" diameter.

Does your speedo read correctly with those big tires? If so, probably have to get something similar in diameter or tolerate the speedo error.
If not, how much is it off by? Reading low by 9%? Or less?

Frankly I'm surprised that tires that big fit in the front wells. My '01 Durango R/T has 275/60-17s (30.0" dia.) at all four corners, and the fronts - when turned slightly - just clear the fender flares at the forward and rear parts of the front wheel well.