Single plane vs dual plane intake

Mainly all of these intakes need work cause they hinder any decent set of cylinder heads. A port that flows 278 only flowed 246 cfm after bolting a ootb victor 340 i bought off here in 2010 onto it.
Gasket match, semi deep runner porting, narrowing the dividers at plenum and bull nosing under flange and it flowed 265 cfm.
Nothing outrageous, but well needed.