The carb they used was on an engine dyno, not a street car. They tested at WOT, no thought given to throttle response or anything else.

On my LA 360, mild setup, I tested a 600 and a 750 cfm carb in my daily driver. The 750 could peg the 125 mph speedo. The 600 could not but in all other areas, again on a daily driver, was superior. Better throttle response, better get up and go, better mileage. But anything running 4.30 gears isn't a daily driver even with an A518, imo.

It really depends on how you are going to use the vehicle, imo. Daily driver or weekend cruiser, 600-650. Race car 750, weekend warrior, well I'd probably go with the 750 myself.

Oh and saying whiplash cam doesn't really help, there are four possible whiplash cams that can be run, two specified for the Magnum and two for the LA, all of which will work, all with different specs.