Are your headers around 1 7/8" tube size. or 1 3/4" what have you played with in tuning of your headers. Been playing with headers by ED info packet and getting schooled up on some header sizing.

 

Carb will be the 1050 dominator (properly tuned), or i may go with a dual carb setup and sheet metal intake (built by me, depends on how different the high port heads are). My headers are 2.25" primary and 4" collectors, they are headers I built. They work pretty good (size them like you size a carb on these 400's, what seams wayy to big for any other motor works about perfect on the 400).