Kinda depends on year, I think.
I sold a friend of mine (1970 Impala) a kit #6770CBK-S that I got from CPP
They mention a part #6568SP for a 1965/68 reconditioned stock spindle ... but didn't have anything available at that time. Customer made a trip to a local boneyard and was able to come up with them ... and everthing else worked fine.
I can't seem to find out what diameter the rotors in the above kit are, but there is a tech article
that says you can use 11, 12, or 13" rotors on stock spindles. They also say that the 13" ones are designed to fit Chevy 1/2 tons with "PBR" calipers. ??? Read the article and see if it makes sense to you. It might be worth a call to the tech line, and ask them to explaim and confirm all of this for YOUR year.