"Displacement wise, the 4.8L is to the 5.3L what the original 283 was to the 327 small-block (technically 293 versus 325 ci). Given the bore and stroke of each, a better comparison might be the 327 and larger 350, as the 4.8L and 5.3L share the same bore size of 3.78 inches while the 4.8L makes due with a shorter 3.267-inch stroke (down from the typical LS stroke of 3.622 inches). Since the 4.8L and 5.3L share the same block (externally marked 4.8L/5.3L), not to mention the same heads, intake, and other external features, it is difficult to distinguish between the two. More than one enthusiast has purchased what he thought was a 5.3L, only to receive the smaller 4.8L in its place. Internally there are distinct differences, the most obvious being the use of flat-top pistons in the smaller 4.8L."
Quote from Motortrend
Here is the link for the whole article
https://www.motortrend.com/how-to/4-...e-ls-slugfest/
Go with a 5.3 or 6 liter. We have a 5.3 in my sons 86 K10 with a BTR stage 3 cam, Edelbrock Pro Flo 4 fuel injection in front of the 700R4 and it rips.