Well theres loads of info on thirdgen.org on how to make extra power from your 5.0. Heres a few ive done
Bump up the timing, stock is probably set to zero or worse, when idle should be advanced maybe 4-10 degrees it depends on engine.
Helpful to have a diagnostic scanner so you can see if your getting knock, the ecm will retard the timing if that happens but its a good idea to avoid it.
Larger airbox, theres twin snorkle air boxes around, mine came off a dodge ram from the states was cheap and i knocked of 0.5 seconds of my 0-60 with it. Have the 1/4 mile times to prove it and was consistant as well.
Cooler thermostat, these cars came with a 195 stat thats way to high, go for a 180, 160 is too low really.
Finally and most important is the exhaust, i havent worked on my yet since i want to rip the whole thing off and go stainless. I have the headers i just dont have a garage i can work on for months to weld up the pipes. Some magazine managed to gain around 60-70 hp and torque from just changing the exhaust to long tube headers and a 3" pipe.
If you havent bought it i wouldnt bother with a 350 really a 305 you can make over 400hp with decent parts on them. Theres a racing league in the state that does just that, standard block and crank just has aluminium heads, intake and a decent cam.
Case is a 5.7 is a bit small, really not going to see much difference, unless u make it into a 6.6.
If want more hp just go mad like me and get a 7.4l
