I wonder if the Surly site has typos, I'll measure it later. Again if you're looking for a 58cm the differences may not be as marked as they are in the 56cm version. I found 1.5" tires too hard unless they were light/supple tires at just the right pressure, the surprising part though was how low the rotational weight was wrt accelerating, but that's a five year memory and 30less pounds ago. 2" tires seem like overkill for paved roads. It seems like you're deciding more towards a load carrier while your original post implied more unloaded use.

yep, 42.5"