1/2" breaker bars and extensions aren't going to cut it. No matter the brand.
I use a 3 1/2 ft. Snap On 3/4" drive breaker bar with a 3/4" to 1/2" adapter with a 36mm Craftsman "regular" socket. Even with 3.5 ft. of leverage, I usually have to use my entire body weight and then some to get the nut to break loose. That's a good 600+ ft*lbs of torque.
Note that I have twisted 2 or 3 of these 3/4" to 1/2" adapters in half.

I don't have a source for Snap On parts where I can order a 3/4" drive 36mm socket.
