Ahh, the old Intergalactic Back Order thing.
No the calipers are different. They will have different characteristics, which is likely why the dealer is refusing to install them. I am sorry you're going through this - since the human malware epidemic, society has been run by people with dark triad personality types that don't care about the person actually purchasing their goods. It's like this with every build right now, not just GM.
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1988 9C1 - Modified LM1 @ 275HP/350TQ - TH700R4 - 3.08 8.5" Disc Rear - see it at
http://www.silicon212.org/9c1!
2005 Crown Vic P71 - former AZ DPS - 4.6 liters of pure creamy slothness!
1967 El Camino L79/M20 old school asphalt raper
Remember - a government that is strong enough to give you everything you need, is also strong enough to take everything you have.