[Mus408]

I opened up the plenum bores to match the spacer and to give more plenum volume since a 427 sized Windsor with good heads is really a big block with same bore/stroke as an FE 428.
Yes that manifold picture...not mine... shows flow numbers but not sure if that was before or after porting.
The carb setup that I later came up with is a Holley 1850 that I modified to 650/660 CFM specs using a 750 base plate. A special blend cut at base of carb body is needed.
The rear carb is a 4224 660 Center Squirter that I setup same A/F specs like the front carb.
When cruising around at less than full throttle you are using the primary barrels of the front carb. When you go beyond 40% throttle travel the custom linkage starts to pull in the rear secondary carb which being the 4224 has a very quick secondary progression at almost 1 to 1 and center squirt takes care of any bog. The front carb vac. secondary with light spring comes in at same time.
Weighing less than 3000 lbs. with me in driver seat and over 500 lbs. ft. torque with a manual trans the response is quick with no bog.
Would be great if one of the custom carb shops could build small bowl double pump carbs for inline Holley use but so far nothing for that.
Works great with this intake manifold!