I've seen A LOT of posts about making HP with a 318-So why is it so ???

My 68 Valiant came with a 380hp crate 360 and 2.96 gears an a 2800 stall on 245 tires.
It's pretty soft under 2000 rpm, in town under 40 mph have to drive in 2nd or it lugs it still gets up and goes but the 2.96 are definitely holding it back. Need to get it up to 40 mph in 1st then give it before I get any real sense of the power it's got.