There ya go.

4.3L - Cast EVERYTHING (virtually)
5.3L - Cast block, aluminum heads, plastic intake
5.7L - Aluminum block & heads, plastic intake.

My truck also seems to sit NEARLY the same height in front. I have spring clamps bolted to my rear leaf springs. They drop the back end slightly, and preload the springs too. Barely helps with traction. That's a poor man's traction helper right there!