The lightning cam puts the power curve close to where I want it. More duration would move the power curve to a higher RPM. If anything, I want it lower. It seems nearly impossible to get hotrodders out of the high RPM high HP mindset. As I said, the 300 inline 6 had an ideal power curve with maximum torque at 1600 RPM and maximum HP at 3800. I want the same with 2 more cylinders and nearly 100 more CI. 21 yrs. driving trucks taught me high RPM is useless. As for headers I've been there done that. They are only helpful over 3000 RPM. They cook the engine compartment and they are noisy. UPS experimented with Borla stainless headers in a couple thousand trucks. There was no improvement in fuel economy. I drove one and was happy when they went back to manifolds.
My 351 only rarely winds over 3000. On the interstates I'm only turning about 2600. Around town I average about 2000. Merging on the highway is the only possible place to use more HP.
The Holley 4010 is a cheesy copy of the Ford 4100 and they never made a smaller version than 600 CFM. I chose the 480 for throttle response, fuel economy, and off road operation. It's simply the 2bbl OE 289-302 EB carb with 2 extra barrels, and looks as original using the same air cleaner, fuel lines, and linkage.
After owning 3 stock EBs, I know I want it to look like EBs did while they were in production. These are historic vehicles that worked amazingly well as built. They don't need to be turned into monster trucks, crawlers, or race cars. There are areas that can use improvement but the do anything utility vehicle has to remain so.