I need engine help

[SRVBLUES64]

I have a 350 in my 66 chevy truck it seemed to be laying down when accelerated or put into gear. this is what we have done, vacuum checked perfect all electrical checked paerfect distri and other ohms that you can check. I even put a new hei accel dizzy on we timed it with a light but its just keeps laying down Im thinking timing chain gears they are new but that the only thing I can thing of now any thoughts any one before I rip it a part to look at the gears??????