A 'healthy' cam, though could really hurt the low end ona small motor like a 5.3. I know the LS6 cams are popular as a cheap HP adder, but they cut out a lot of tq below 3000, according to the side by side dyno plots I've seen. Likewise, the factory intake is designed for low end torque. So he's probably lost a good 50+ft-lbs down there in the crawling ranges, which would put it not all that much above a 4.0...
The LS1 woudl be ~90 lbs lighter, due to the aluminum block, if it matters to you. Although aluminum block 5.3s (L33s among other), and 6.0s (LS2) exist as well.