Best cam for a 5.3

There's no single best cam; match it to your goal. Here are proven combinations from Speedway Motors' 5.3 build recipes:

• ~400 hp street/truck: BTR Truck Norris cam (212/22X°, .553"/.553" lift, 107 LSA; $409.99 at BTR) with BTR springs. There's an "NSR" (no springs required) version that works with stock springs. Speedway's junkyard 5.3 made about 430 hp in their C10 project with this cam, lightly shaved 706 heads and new valve springs.
• ~450 hp: Edelbrock Rollin Thunder cam, PAC 1218 springs and a trunnion upgrade, with an Edelbrock LSX 92 mm intake and a 92 mm throttle body.
• ~700 hp boosted: Elgin/Sloppy Mechanics Stage 2 cam with LS7 lifters and trays, head studs and a new timing chain.

Gen IV 5.3s with AFM (LH6, LY5, LC9, LMG) need an AFM delete before any aftermarket cam. At around 400 hp you're near the limit of the stock injectors and fuel system.