Engines with lack bottom end power?

Tuning is important but especially if it's a carb'd application, air speed and booster signal at lower RPMs are crucial. They are directly related to how responsive an engine is under light throttle. Also when larger amounts of valve overlap come into play the tuning of the exhaust can make a huge difference in torque below the peak RPM. Lots of tests showing how collector extensions on open headers give a massive improvement in torque and the longer they get the lower the RPMs where torque is increased.

In your case, you aren't feeling the "380 lb-ft at 2500 RPM" likely because when that figure was recorded by whoever did the testing they either had the tune dialed in perfectly with a perfectly configured carb for the application or were running sequential multi-port EFI. IIRC the 380hp Magnum crate came with a single-plane intake and fairly large cam with only 9:1 static compression which is not a combo that's easy to tune for low-RPM response and performance with a carburetor. Especially if that combo is run with exhaust manifolds, there will be lots of reversion at lower RPM and low-end torque will be garbage, along with poor high-RPM torque/power due to restriction.