update: So she still pinged at WOT in the 3000-3500Rpm range. timing was backed off to 12 initial and 28 total. Good driveablity w/ 10 city and 12 mpg Hwy but stomp on her and she starts to ping in that range and would get rich (9:1 afr) and eventually stumble. I kept backing off secondary jets (116 to 107) and went through all sorts of combos of metering springs and rods on my edelbrock AVS 800cfm. Nothing seemed to help. I adjusted the air flap on the secondaries (thinking it might be opening too slow). No help.

Finally, called company X to discuss the possibility I needed an 850 cfm since that is what the butler guys said it would need, but I was hesitant since I had a good 750cfm which 'should' work. company x said, "OH NO, you need no more than a 750. So conflicted again about spending money on yet another carb, I turn to a friend that had just removed a mighty demon from his 540ci chevy and coincidentally it is the same set up he has on his 428 FGF (bored to 440). So I, being in between this two builds give it a try.

Put it on, fired it up, and it ran better immediately. Took it for a drive and ping seems to be gone. No loss of driveabliity at low speeds and pulls harder/smoother at WOT. AFR is maybe a hint rich. My vacuum is around 7 at idle so I changed the power valve from a 6.5 to a 3.5 this morning. I will fire it up tomorrow and see how she does.