My 383 is weak!?

I had a 383 built just like you mentioned except it had a .484/.484 Mopar Performance cam, Performer intake, 750 cfm holley, headers, and it was nothing close to weak. Also it had stock 383 heads... I wonder if the 440 heads is killing it? It was however in a 68 Charger with 2800 stall converter, and 4.10 gears. If your motor has good compression and is running like it should (no bad cylinder, good spark plugs,etc... healthy) then you might should checking to giving it some more gear like previously mentioned. If you go bigger on the cam you might as well go with a stall converter so you will have good street manners with the truck in gear and idling. A stall converter will get it out of the hole quicker because you will building up more RPM coming off the line.

What gears are in the truck?