Rear End Swap 7-1/4" to 8-1/4"

I Did the same but I am Having a problem that the brake pads that I ordered are too big. I dont know what is happening. The pads and the Drums are of 2 1/2 in. Does yours take the same or are they 2". This Is driving me crazy. I got a diff that only had the back plates and I guess that is why I am having the problem of finding the right ones.I ordered the same for a 1973 Dodge Dart Sport and Advance says that the 2 1/2 in are the right ones. Help