The high riser heads should not be a problem. Actually the med-riser heads flow very close to the same CFM but as they are a lower profile they became more popular.
It's not the "heads" but it could well be your cam profile. My 427 is pretty darn "radical". High riser heads, wild cam, tow four barrels. 1/4 mile in the 11's, the car is VERY fast. Pulls strong from down low, med rpm and up to 6500. Actually I shift at 6000 as I've found about the same 1/4 mile times shifting at 6500 or 6000.
I don't know what the heads are worth but I found out the 2X4 intake manifold (Ford OEM) is worth about a $1,000. I'm thinking aobut "experimenting" with a single four barrel carb and am looking for a high riser manifold to match my heads. Wanna sell yours?
Oh yeah, I'm pretty sure your intake manifold is the problem, better dump it right away.
