This 454 motor was just rebuilt using a 292 comp cam dart iron eagle heads and intake.  850 holley double pumper, hei pertronix distributor, hooker headers w/ 3" exhaust, 4:11 gears with turbo 400 tranny.

The engine runs good at idle but when I put it in gear it barely want to go and has a lot of hesitation.  I have moved the timing back and forth with no help.  Any help would be appreciated.

 

Could be a vacuum leak or carb issue  

you have a t400 gear box the convertor may be not matched to the engine it is like appying the cluch to late or early to help the car move off
some quick tests start the car and put your foot on the brakes and put gear box into drive then aplay the acclerator and see where the revs go up to that will give you what stall it is.
do not go pulling your hair out yet