The size of the bore is about 110 mm which is larger than the typical GM and Chevy hubs which are about 90 mm under. In order to get the wheels to become flushed exactly you need to determine what the exact size tire width of the new tire and compare with the stock width tire which was 245. And I believe the stock tire even sunk in (don't remember by how much) from the wheel fender. Once you find the numbers accordingly, you'll need to factor the offset distance of the new wheel and compare to the stock wheel offset of 38 mm. Anything lower than 38 mm (positive) will cause the wheel to come out further than stock. I had Borbets with an offset of 0, I believe, and 265 wide tires which brought the wheels out about 38 mm or 1.5 inches from the fender. But, I'm not sure about the exact measurements although I'm sure they were close to my estimate.
You also need to take to account of the rim size since the stock rim is 7" and anything wider will affect the offset formula.
Another thing you need to be aware of other than the center bore size is the center ring opening in the middle of the hub. Some wheels taper enoough to interfere with that area and won't allow you to attach the center cap of the wheel if there is one. It's a lot of trial and error in this process and can get frustrating as you may think that it will fit this time around only to find out that it doesn't. I suggest going to a wheel shop and have them order the wheels specific to the truck so mistakes will be minimized.
Good luck and hope this helps from one wheel searcher to another.
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