It's really what you want in the end. The Six Pack replica will probably cost you a bit more than the $2700 mentioned above by the time you get all the odds and ends required for the install.
When it comes to bling and popularity, it will be almost impossible to top.
The 440 six pack came with a 350 cfm carb in the middle and a couple of 500 cfms on the end for a total of 1350 cfm. That equates to approximately a 950 cfm four barrel carburetor. The six pack intake probably is not as well balanced with regard to air flow as a modern four barrel and I think that a good 850 carb will perform right beside a well tuned six pack and probably better than the average one going down the street today.
An 850 double pumper would be my first choice as it will perform just as well as a smaller carb on the street if you learn how to use your foot when launching from low rpm.
If you are going to a manual transmission, the double pumper would work even better or if you have a higher stall converter behind the 727, the same applies.
So...if you want bling and don't mind the cost, the six pack is the way to go, imo.
If you want to save some money and simple performance is the goal, then an 850 cfm Proform double pumper would be the way to go.
Personally, I would probably install the SD with the 780 cfm Proform for the moment and put my money toward the transmission swap and other things for the moment and then go for the 850 whenever the time feels right. The 780 can handle 500+ hp when jetted right if the engine can give it to you so it should be a big improvement over the Carter.
