I'm assuming you can use a deed and a called shot at the same time, but i'd like to make sure. Would it matter if you have the Improved Called Shot feat?
Also as an aside, this would be stupid but also amazing: if I have greater called shot can I use it with siege weapons? Please say yes.
Depends on the deed. Greater Called Shot should work with any attack-based deed as it lets you make a called shot whenever you could make an attack. Otherwise, it works only if the deed modifies an attack as opposed to being its own action. You could combine Ricochet Shot Deed or Twin Shot Knockdown with called shot without issue, but not Leaping Shot Deed (that's its own full round action, so would require GCS), Targeting (same), or Cheat Death (that isn't an attack at all).
I don't see anything preventing siege weapons from using the same rules, provided they are direct attacks rather than area effects.