As they say in the military, "Never turn down a combat assignment." If they offer you a 767 class and you want the Whale, TAKE the 767. At some point (after your seat lock) you can bid whatever you want.

If you bypass, they may not have a class again for months/years. And most likely, they'll have a system bid before the class and you may be looking at the 767 anyway.

If your target airline offers you a class, TAKE IT! Ask questions later.