I have progressive 3x1 on my truck. See the Rides section for pictures. I originally tried to use that "CL-3B" linkage shown, which is intended for flathead Ford V8's, but I found it would be harder to make that work than making my own. Making adapter plates to turn the carbs 90 deg. is necessary. The rod ends, stainless steel bar stock, LH dies, etc.. can all be ordered from McMaster-Carr. The real trick to actually making it run correctly is to remove the power valve circuit from the end carbs and get the throttle plate to seal up enough to prevent surging at an idle. I didn't have good results trying to run them in stock form. Running Carter W-1's would probably be a better choice than the Rochesters because the power curcuit on the Carters is not operated by vaccuum.
The main drawback I have right now with it is that I can't really hit all three carbs until I have about 1800 rpms or so. It's like the old 348 Chevies and Olds J2's with the vaccuum operated end carbs. That was so you had enough demand to be able to use all that cfm. Too much at the bottom end and it will fall all over itself. At least that's the results I've seen.
