8 1/4 rear with pinion snubber

I have a 67 Dart with a 8 1/4 rear sure grip. I have a pinion snubber but for the life of me cant find to much info. Im in need of the rubber. Is it the same as a 8 3/4? Im going to need one eventually and when i search all i can find is 8 3/4 rears with them. Thanks in advance.