[Super73]

Ask your self this question (And answer it honestly): "Am I going to modify this motor or leave it stock?"

Answer no, buy the 4.8..

Answer yes, ask your self: "How far am I going to go with the modifications?"

Answered as bolt ons, you can go either way, but the 5.3 is going to give you more gains with the same parts.

Answered internals, IE Cam and possibly heads, you definitely want the 5.3 over the 4.8. The added displacement is going to help tame most any camshaft you put in there and will provide you better driveability than its little brother with the same mods.

Answered rotating assembly plus head/cam at some point, then it doesn't really matter. Yes the 4.8 comes with the short stroke crank but the blocks are the same. You could find a longer stroke crank next to nothing at a later date or if you are going to go 4" stroke someday it won't matter. But if you plan on going this route, get yourself a 6.0 for the simple fact that the 4.8/5.3 bore is small and really hinders head flow by shrouding the valve, killing power NA in comparison.