Today folks can gain as much as 20-30 hp with a tuner, aftermarket exhaust, and premium gas.

The little 2018 Ford 5.0L now puts out 460 hp and 420 lb/ft of torque with stock cams and tunings in the Mustang (395 and 400 in the F150). The block is capable of 1000 hp so the normal way these days to add hp on the 5.0 is to slap a supercharger or turbo on it. You don't have to dig into it to change cams and the heads are pretty slick already...although a cam change can make forced air more efficient.

__________________
I love sanding.