The intake manifold gaskets on the 5.3 are different then the LS1/2/3/7 and are prone to leak. Also the LS7 lifters and valley cover need to be replaced in order to delete the AFM, not just because you will have them apart. I suppose you could reuse the v/c, timing cover, exhaust, and w/p gaskets but those aren't exactly the expensive part of the build so you have weigh your risks.