Swapped out a 750 Holley for a 670 Holley, aluminum with four corner idle.  Holy crap!!!  Drivability improved 100%!!!  I am impressed with this carb. I put a 7.5 power valve, 68 primaries and 76 secondary jets.  Left the stock squirter.
This thing drives great, and might just help with gas mileage. 

I was looking forward to burning regular gas in the 69 on the bash trip but will just have to “pony up” for premium. The 66 is being readied for the trip as of today.  Plan will put 3,600 miles on it.