Hard rto say.Odds are even the dry scrubbed rock is gong to have junk inside it that will have to cook out and cycle through. Even the sand is gonna have somewhat of a cycle......I would place the old dry ropck and sand in the tank to begin with and start the cycle and see where it goes from there.....No sense taking a chance on putting a good cured piece of LR in a tank thats just starting a cycle only to have it go really high and possible kill off some good stuff on the rock you buy....so once ammonia levels etc start to come down to lower levels then put the piece of LR in the tank...Depending on how large those pieces of dry rock are, I would probbaly start off with good live rock and sand, and add a piece of the dry rock a lkittle at a time, but it would really depend on how large those pieces were in relation to the piece of LR I started with initially.
