I am wanting to swap the fronts to LS1's but if the rears are not much better than I will just keep them and save some work and money.

 

I dont think the brakes themselves are much if any better with the LS1 setup, however, the parking brake system on the LS1 setup is much better in my opinion. So switch to the LS1 setup though it's more involved than just calipers and rotors. It is somewhat indepth.