It could be possible to create a differential patch from an earlier install and a current steam install. This patch would likely be at least several hundred MB in size, less than redownloading the game but more than your average patch. You'd basically need a 1.60 install and a 1.62 install, then create a differential patch between them with something like
WinMerge. I've no idea on what BiS policy would be on distributing such a file, as you would essentially be sharing parts of both versions - I suggest that you check with them first.