74 Duster 4 banger Street/Strip Build

My OMNI dyno'd last year at 577whp/551trq. I think I can make more with a better header and intake setup. The OMNI is VERY cramped for room under the hood. Video here:
[ame="https://www.youtube.com/watch?v=ot3Z96JkM-4"]Omni GLH Dyno 577hp 552 ft-lb - YouTube[/ame]
That one is kind of poor quality. I'm driving, and my buddy took it with his iPhone.
Here's another one with the dyno owner filming with his phone:
http://youtu.be/HQNEPtHxA4w?list=LLNuM9ngFrsSS31cA7ol57ng

Hoping for a reliable 600/600.