273 said People build 400-500+Hp NA LS 5.3l all the time and even do 400+ NA LS 4.8l build a 318 like you would a 340 it’s just got to spin slightly higher need a bit more gear and stall. It all comes down to cylinder heads and right cam carb intake exhaust cr to support it, displacement will decide what rpm you’ll make power. Click to expand...