How much part interchange is there between the 4.8 and 5.3? Specifically, can the heads interchange, and are there any significant differences like valve size, port size or chamber volume.
There's everything from Cast Iron(Seriously cast iron?) to aluminium bodies, variable timing, different bore sizes and so on...
One compact version for a FWD car even has a dfferent head bolt spacing.
https://en.wikipedia.org/wiki/LS_based_ ... ock_engine
That page should at least tell you if the cylinder bore is the same or not.
(If it isn't the same, then forget it.)