Makes sense on the spindles.
Brembos are great brakes and would make for a neat modification. Essentially, there's a tradeoff where you carry an unnecessary amount of unsprung weight around for brakes you don't utilize to their full potential. G-bodies are heavy, and with the proper chassis can use as much brake as they can get in an all out handling/racing application. If you are going max effort to get the widest tires possible under the car (say a 255-275 front and 295 or wider rear from cutting fenderwells and notching rear) that have a soft treadwear rating (200 minimum is typically accepted for most street car pro-touring style events), the brakes may certainly come in handy. If you have more brake than your tires can handle regularly, those no point in spending the extra money on them and accepting the weight penalty.
That's obviously my opinion, I think the CTS-V brembos look great and should work well based on the Nurburgring thrashings they put those heavy cars through. I also didn't realize when I made the post above that the new CTS-V brembos were going so cheap as take offs... when you were talking ZR1 brembos, I also assumed you were looking at spending $8-9k on a set of brakes. For $1200 I'd definitely consider giving it a shot. I've seen some threads on either pro-touring or lat-g where somebody engineered a custom parking brake solution as well, it was pretty neat. Good luck with the project, hope it works out well for you!
