The advice isn't based on anything except what will work right out of the box, and the smaller 1.08's are better only for one reason...they won't need rejetting and a raft of anoying changes.
That 1.33" venturi carb will work, but has to be recalibrated to suit. Some of the work on getting power valves and jets and other work done on these carbs is pretty high brow
Based on the size of the carbs alone, the 424 cfm is much bigger than a 1.1875" 350 cfm Holley, yet smaller than a 1.375" 500 cfm. As you will note from was111's work on his modifed 200 Mustang, a 500 cfm carb can work just fine on "warmed up"I6.
The good thing is the 1.08 and 1.22" Autolites are quite small carbs, which are already jetted lean for 260/289/302 2-bbls. Some versions (California 1966, and all 1967 on version sof the auto 289) are annular discharge, and they were well ahead of Holley for general design smarts.
If your likely to see more than 140 hp net (that is, the carb comes off a car which has more than 160 hp gross) then go for the bigger carbs bigger than 1.08. If not, then stick with the Falcon Six recomendations.
