ok so i pokerflush123 found how to carry a class through on mw3, you dopnt keep your pro perk or attachments though so sorry about that,,,,
ok heres the steps
Step 1 get to level 80 where you can prestiege
Step 2 get a mate to host a lobby
Step 3 tell him not to do anything yet
Step 4 choose the class you want to take over (i recommend taking gold camo over)
Step 5 click copy on the class
Step 6 hover over any of you class in which you want to copy it over to
Step 7 get your mate to find match, then ask him to back out when in matchmaking
Step 8 you should be able to move around the multiplayer menu, go prestiege, when you have prestieged it should let you choose which class you want to copy if not press B after prestiegeing
Step 9 press a on the class copied to.
Step 10 play a game online and you will see that you class is already unlocked even before level 4!!!!!!!!!! please try get this a sticky, message x Sprokey x on XBL for help or add pokerflush123 on skype