Need asap rear cover 7 1/4rear end

found out something new the dak used a differant 7 1/4 rear, 87 to96 it big like a 8 1/4 but has squard sides. look like pull a part this week end.i was going to take my 8 1/4 in but from looking at the truck and the gasket listed for it. they are differant.larry shepard said there was a differants between.