Crying shame that you gave up on the AFB and went with the Holley.

I have owned AFB carbs since the late 80s and greatly prefer them over the Holley stuff. They tune nicely and have great street manners.
Yes, I have been able to get a wee tiny bit more power out of a Holley but it comes at great cost to mpg and street manners. I've even run the dreaded 750 AFB with good results.

It's your car so do what you want. In my opinion it's kinda silly to go through all that trouble when a 3/8" spacer will likely cure your ills.