If your vehicle is currently running with the original Rochester, you might try:
(1) Run three 0-60 timed runs with the original carb, and compute an average.
(2) Add the two-barrel with the 2 -> 1 restricter (er, adapter).
(3) Run three 0-60 timed runs with the 2 barrel, and compute an average.
(4) Compare the average computed in (1) with the average computed in (3).
(5) Then you know the effectiveness of your change.
Jon.