Both of my A2's have the 16.5" rims with 33" tires with a straight axle. The best that I can tell is that the A2's have Surge brakes and later A2's got a more reinforced cargo bed with corner lift points.
If you have A2's with the 37" wheels on them, chances are they were changed out before the sale or by a motor pool with only 37's to throw on.
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The corner lift points are common amoung the A2's and 3's according to the service manuals. (Speaking of the u bolts at the corners.) The manuals say the A3's have a 4" frame while the A1's and 2's have a 3" frame.
When re-reading the manuals last night I came across a gov't publication that cites the difference between the A1,2 and 3. No mention of bed size differences, but it did cite straight axles for the A1's and 2's and "offset" axle for the A3. But my A2 definitely has the drop axle and so did the other A2 in the dealer's yard, along with the 37's. (And the several other A2's I've seen.)
I'm thinking there must have been an ongoing upfit program for the offset/drop axles and the 37's. Here's a link to several gov't publications, including the manuals and the differences between models. http://www.tpub.com/content/misc_manuals_2/TM-9-2330-202-14-P/index.htm
JPK