Re: 4.8 bore size
A 4.8 has the same bore as a 5.3L with a small stroke. So you might as well just get a 5.3L crank, rods an pistons. Or a whole engine! If you at it get the 6.0L or the LS1!
I would imagine you coudl overbore a 4.8L .030 over or more maybe .060?
Bret