Bill, that's pretty interesting information. Can you give any more info about the J56 Brembo 4 piston calipers? Like what year and model to look for?
Here's a capture of ongoing discussion on a Caprice PPV Forum on Facebook...still waiting to see if the PN's for the calipers from that discussion (using a 6th Gen Camaro upgrade kit) can be confirmed. I use Rock Auto as a search/reference, but still need to talk to the dealer to see if I can learn more.
"The current CTS uses a 345mm rotor that is common with Gen6 Camaro, with the RPO J56. RPO J55 is a 321mm rotor. In similar fashion to the brake kit that Scott purchased, it shows that the J56 spec for CTS uses what appears to be a Brembo caliper, as shown here: https://www.rockauto.com/en/moreinfo.php?pk=6113247... "
"part above is left side, priced at $153.79, with no core (looks like this is incorrect)--translates to GM 22796239 or 84089036--I'd have to research the other side at a dealer. The Camaro equivalent is not easy to deduce from the info at Rock Auto, but the Gen6 Camaro SS does list the same (size) 345mm rotor with brake RPO J6G and Brembo calipers."
GM 84089036 caliper
To be clear--re-stating earlier comments--these 6th gen calipers for 345mm rotors will work on G8 & PPV, but the rotor is the part used on PPV, NOT what is used on 2016 & newer Camaros.
A PPV owner has acquired this kit, and reports that the calipers in the kit fit on the PPV 345mm rotors. Details and photos still to come, hopefully. For G8 owners, the one thing that would have to be done is to enlarge the holes on the front knuckle/upright for the larger (14mm) bolts that secure the calipers. PN's for bolts TBD
at this point. Hoses in the kit probably will not work, but my experience with PPV, G8 and SS tells me that it's likely the stock hoses or the Russell G8 hose kit should work.
The upgrade kit may be the cheapest way to get the calipers, since it sells for about $400, and includes calipers, rotors, hoses, and fasteners. PN is 23245470 - the rotors alone (one-piece, not two-piece as shown is some listings) sell for more than the complete kit--about $325 each!
Link to kit
(when viewing this listing, click on photo on the right of the 3 shown for the correct kit with one-piece rotors)
Other Names: Parts Pkg, Brake Upgrade Kit, Brembo 4 Piston Front
Brembo(R) Performance Front Brake Package (Four-Piston Calipers, Camaro LS/LT)
True stopping power! The Chevrolet Performance front brake system features Brembo(R) four-piston aluminum calipers with performance brake pads and 13.6-inch x 1.2-inch (345mm x 30mm) vented and slotted Duralife(TM) rotors - the same size as the Camaro SS! The Duralife(TM) rotors feature a hardened surface to reduce corrosion and provide quieter braking with less vibration. The kit is a direct replacement for the original front brakes and includes low-expansion front brake hoses, all necessary hardware and installation instructions. It is available for Gen 6 Camaro LS/LT models equipped with the 2.0L Turbo or 3.6L V-6 engines.
Some searches for this kit say DISCONTINUED but we're checking into that.