1 7/8 inch manifolds are on there more. 340 hi po and a 360 magnum (I believe) are 2 1/4 and 2 1/8 respectively. I would expect more performance gain than 5-7 HP, wouldn't you think?
There's a manifold shoot out on a mild 360 (300hp) With 318/360/340 and magnum manifolds and there was 5 or so hp from lowest to highest flow which was a combo of 340 and magnum manifolds. Even shorty headers only added like 10 or so hp and full length was like 15-20 hp If I remember right.
EQ are decent price high flowing magnum type head can come in LA intake bolt pattern.
