Engines with lack bottom end power?

Agree

What's getting me is take the 5.9l magnums crate 300 hp vs 380 hp for eg..
They both make about 380tq at 2500 rpm obviously above that the 380hp has a better power curve. and under 2500 rpm I doubt they vary to far from each other and even with stock stall and part throttle wouldn't spend a lot of time down there in normal acceleration while driving.

So since both these engines make similar low end power why would the 300hp be ok with stock stall and highway gears and the 380hp needs more gear and stall, why I have to cruise in 2nd around town with my 380hp crate, most would say low end torque but since they have similar power down low lead me to believe it ain't a torque/power issue but a cam spec issue.

And the more I look the more it seems like most built engines make good enough low end power.
I think the assumption you are making about the 300 and 380 magnum crate engines having the same torque curve is wrong.

Big difference in the two cams in these engines, so likely a bigger spread in the low end torque curve than you are thinking.