Yes you can and in fact you SDC directly into J (as you are ticketed in J), not into Y and then hope for an upgrade. Most agents don't know this and will offer to SDC you into Y. Others will try to tell you that award inventory must be available on the flight at the level (low?) you paid and that unlike the case in coach, you cannot SDC into any available seat in the biz or FC cabin. This is wrong. Be prepared to call back multiple times and/or fight. (Even the supervisors and redcoats don't know the rules.)