I didn't think it would be that easy but checked anyway.
Since 8.5 G-body axles are rare and expensive I'm going to install a Ford 8.8 and would like the front to be the same pattern without adapters. I did come across a set of axles for the ford that are the chevy pattern but the axle I'm buying already has Yukons with the 4.5 pattern in it so I figure I'll swap the rotors.
any place that sells circle track parts will be able to set you up with a set of "metric" rotors that have that bolt pattern- and they will probably have 1/2" studs that match your 8.8 rear end..