I have a dual quad '58 era iron single plane intake with a pair of 4131 OE 3 step AFB's converted to eddy 2 step rods/jets going onto a 451 so I will be learning how to tune them also (the idle circuits are my concern). I'd set the initial with the vacuum gauge method then shorten the slots to get 36 total then check/correct a few things on the carb setup: floats not waterlogged/correct float level settings/fuel psi within limits. Then concentrate on the idle mixture screws/throttle position to get it to idle acceptably (which I think'll be the hard part) then play with the springs staying just under the pinging point at WOT up thru the gears. then hookup/tune the vacuum advance if you want to use it (& I would). EDIT Not sure if you need to change anything with the holes in the throttle blades or not