Fly AA J all the way

I am planning a trip to NY at the end of March. On my dates, I cannot find a single C seat LAX-JFK, but I can find plenty of A seats to SFO on the 763s. I actually like the idea of F on a 763 better than J on a 762, but I'm a little concerned about a SFO connection.

Is there anyone here who chooses that route? My biggest concern, obviously, is a weather delay that would cause me to miss my flight to JFK. Should that happen, would AA reroute me directly out of LAX? What if no J seats are available, only F, would they give me one, or would they tell me no dice because it's a weather delay and they aren't really obligated to get me into a premium cabin until there is room on my original route?