So I was thinking, I have an 01 Buick Regal GS and 98-02 f-body front brakes are a common upgrade on these. They are literally a bolt on mod. I did it and conformed its a direct bolt on. Now if these are a direct bolt on, why wouldn't the 12.7" GXP front brakes (also a bolt on mod for my Buick) bolt onto a thirdgen that has already had the 98-02 f-body front brakes added? Anyone heard of this before. The GXP im talking about is the late 2000's grand prix with the FWD 5.3l. The calipers/pads look very similar to the 98-02 calipers/pads, just with a bigger 12.7" cross drilled rotors. I think it would be a nice upgrade for someone that already has the 98-02 f-body brackets/brakes on their car, and looking for alittle more brake. It should bolt right on.

 

did they go to an aluminum caliper on those, or were they still cast iron like the older Impala/Monte Carlo?

one issue might be that the rotors won't fit over the 5X4.75" bolt pattern... the LS1 F body/W body 12" rotors have bolt holes that are drilled oversized to allow them to fit both the fwd and rwd bolt patterns- the fwd pattern puts the studs towards the inside of the holes, the rwd pattern puts them towards the outside of the holes.. the GXP rotors might not be drilled like that... but if that's the only hurdle, then 5 minutes with a bigger drill bit takes care of that problem..

 

Yes, the GXP calipers are aluminum, dual piston. They look very similar to LS1 calipers. I believe they are made by PBR also. I'm not sure what the piston size is on them, I'm going to try and find that info. The wheel stud holes on the rotor will have to be drilled bigger, but like you said, 5 min fix.