Differences between B and B series II excavators

Hi folks, I've searched around the net on different occasions but I cannot find anything that lists the differences between the original B and the B series II CAT excavators. I've often heard anecdotes that the B series II were much better than the original B's yet no one I've spoken and nowhere I've searched can tell what was changed between them. I'm particularly interested in finding the difference between the 345B and the 345B series II as we've a 345B LME in the yard in need of some work. Thanks