Best way to proceed with improving up 427 Windsor street setup

[Ace23]

So while the WWF cage match of the 427 Windsor vs 427 FE is brewing I would like to better understand the following so I can understand the decisions I am making.

ALL QUESTIONS ARE BASED OFF A WINDSOR PLATFORM BETWEEN 427-460CI

*Edelbrock list the Performer RRM Air Gap for a RPM range of 1,500-6,500. Now with this being said I am sure that cam selection , cylinder heads and compression all play a major role. My question relates to a street car that lets say peaks at 5500-5800rpm leaving you shifting at 6000rpm. Why is the dual plane not the appropriate intake? Brent why did you build your 438W with the RPM air gap instead of the Victor Jr?

*2" primary header size. This has been a 50/50 answer that I've recieved. Why on a street car would you keep 2" headers? The only information I have come across that seems to have come from someone who actually had 2" headers was an old post on here were a guy had a Roush 427 and he stated that on the dyno the 2" made a few HP more but only on the very top end......while the bottom end was down 25-50 torque. Is the 2" header design only applicable for cars that would be tracked?. If a street car is setup for 6000rpm why would a 2" primary header size be appropriate.