390 cfm vs super six

Other hurdles to making Hp,for a normally aspirated slanty, are; 3.40 x4.125,long rods,and unequal length intake runners. Plus a really long crank.......,with only 6 cylinders on it. But they can make pretty good low-rpm torque.
If my Volare wasn't such a rust bucket, I might consider installing an 833-od and 2.73s for 65mph=1570rpm. I think the 9.5Scr slanty under the hood could do pretty good with that...... mileage wise.