Yes, the stock is the main difference, which in turn obviously adds a few ounces to the overall weight of the classic. Another difference is the Montana has a threaded barrel and this one does not. If it makes you fill any better, this classic has been to Montana
The Montana is stainless, and this one is blued, right? I could be mistaken.
Edited to add: Is that a stock Kimber barrel? The contour looks a little different to me. Again, I could be mistaken.