I'm a big fan of Q'jets. I probably have 7 or 8 of them. Although more complicated than other carbs, with a little patience and attention to detail they can be tuned to a much finer state than any other carburetor. For all out racing, a Holley type carb is still King, but from stop light to stop light and cubic inch for cubic inch, I've outrun a lot of other cars with Holleys and AFB's installed on them. I may have the exact number you're seeking, but is that number the only one you will consider? The only difference in most of these 70-72 4MV Q'jets were the rods, jets and piston spring, all of which can be changed to suit your needs. The secondary hanger was also a factor, but not a big one.