I'm talking what i know,.... but if it was a bone stock LA cyl head then the Biggest cfm jump is in a GOOD 3 angle valve job and bowl blending the bottom valve cut. The 70 or 75 bottom cut takes a lot of material with it, but it need to be blended into the as cast of the bowl area.
Aka the mcsa is in the bowl area. It could vary well be the case with yours as well.
Just a little food for thought.
