1. yes they do. the 4.8 and 5.3 share the same casting. the
fbody LSx engine use the 4.8/5.3 head to boost the compression
level as the combustion chambers are smaller (62cc vs 67cc).
changing the heads is expensive for the limited gain as the
stock camshaft is limiting your flow. id be cheaper to do a
camshaft swap and tuning than the cylinder head swap.
2. no. itll need extensive tuning with a wide-band HO2S.
3. your OE CID is 293 (4.8L) the .030 over bore makes it
a 298 (4.9L).