2.0 uses sufficiently different mechanics that most systems from the Classic Spycraft books can't be used with it. However, the 2.0 Core book includes a *lot* of mechanics that were spread throughout the Classic line, so you may end up already having what you want there.
There are some less character related mechanics that work just fine (I still use the random tables in Agency and Mastermind) and some that you just don't need anymore (the mastermind system is more complicated and tedious than the SC 2.0 mission design, and a large amount of classes have been converted).
Some conversions have already been done elsewhere. For example, if you look for Mouthymerc's NPC thread in the License to Improvise forum, you'll find most 1.0 NPC classes have been converted to 2.0 NPCs.