It might cost a little more right now, but I would try to get that flange welded back in there so you can use stock exhaust components. If you plan on keeping the car for a couple of years this will be the best thing to do. other wise you be back here when the B pipe rusts out trying to figure out how to replace that part of it. Someone did a ghetto repair job and now you have to deal with it.

But if I can't convince you, yeah can you get a sleeve and two clamps and that should do fine Back pressure is not an issue, it will just be loud if there is a leak before the muffler./