There are ball flange kits out there to replace the standard flat couplers seen on most headers. However, you have to cut off the flange and weld on the new ball socket.
I've thought about it, but never pulled the trigger on it. I've got plenty of other thigns to spend money on to get my car back on the road. In all honesty, Since I began cheking sealing surfaces for flatness and correcting them where necessary, I've not had nearly as much trouble with blown out gaskets, including collectors. Its surprising how some of these surfaces are not as flat as they should be. I'd also think if you properly support the remainder ofthe exhaust system, it will minimizethe flex at the colelctor joint.