L76
Used primarily in light-duty trucks, the L76 is essentially an aluminum block variant of the LY6. Major differences include a higher compression ratio and a slightly larger cam, which boosts output to 366 hp and 376 lb-ft. Like the LY6, the L76 utilizes variable valve timing, but ups the ante even further with active cylinder deactivation. Interestingly, the L76 also powers the Pontiac G8 GT. The car version of the L76 drops variable valve timing and features an LS3 intake manifold, which sacrifices some hp while picking up some torque.

Displacement: 364 ci
Block: Cast aluminum
Heads: Aluminum 15-degree rectangle port
Bore/stRoke: 4.000 x 3.622
Compression: 10.4:1
Output: 366 hp and 376 lb-ft (trucks); 361 hp and 385 lb-ft (cars)
What it’s in: ’07+ Silverado, Sierra, Suburban, Yukon,
Avalanche, and G8 GT

Vortech 4800
The smallest of the Gen III/IV platform is also the least desirable. While they're very capable mills for their intended application and can power stock Silverados to respectable 14-second e.t.'s, their lack of cubes make them unlikely candidates for engine swaps. This assessment is only reinforced by the fact that they're just as expensive as the 5.3L at the wrecking yard. The Gen III LR4 was built from '99-06 for fullsize trucks and SUVs, and was replaced in '07 by the Gen IV LY2. Other than tweaks universal to all Gen IV motors, the difference between Gen III and Gen IV 4.8L small-blocks are negligible.

DISPLACEMENT: 293 ci
BLOCK: Cast iron or aluminum
HEADS: Iron or aluminum 15-degree cathedral port
BORE/STROKE: 3.780 x 3.267
COMPRESSION: 9.5:1
OUTPUT: 270-295 hp and 285-305 lb-ft
WHAT IT’S IN: '99-06 Silverado, Tahoe, Yukon, and Sierra (LR4); '07+ Silverado, Tahoe, Yukon, and Sierra (LY2)