Buy one from Pro-Systems. I have two from them.
Here's a Pro-Systems Carb on a Roush 427R, DA 2100 ft, The car since has trapped over 130 mph with the same carb DA 1800 ft.
http://video.google.com/videoplay?do...e+Exotic&hl=en
My engine came with a double pumper from Roush, I tried a Holley 870 Avenger vacuum secondary(waste of time and money for me) and the Pro-Systems double pumper last. There is zero comparison. The Pro-System carb spanks the others badly. Operation is smooth, perfect at any throtle position any rpm above 1200 rpm(single plane intake) and without glitch. It hits instantly if you stomp it too.