Head Games!

First of all; thanks to all the replies! Second, apologies for the mix-n-match threads. Maybe I can get a mod to blend the two. Anyway...
So here are the basic goals:
12 second/400 HP+ smallblock, pump gas
Here are the specs I'm working with:
*standard weight '72 Duster
*A-833 4 speed
*3.91 or 3.55 8.75 rear end. Planning on starting out with the 3.91
*Headers w/duals
*Single quad, most likely Holley DP
*Dual plane. Have an Air Gap RPM to use as well as others.
*Mopar EI

So, there you have it. Am I missing anything?