The high riser head does exist, and it is quite different from the tunnel port. The high riser heads appeared in 1963 (C3AE-6090-K) and hit mostly race circuits in 63-64, when it was updated to C4AE-6090-F., which ran thru 65 when the high riser was discontinued except for over the counter purchase (which continued about 10 years). It was almost strictly a race head (Thunderbolts, FX cars, etc..) The heads are easily spotted, because they have 2.75 inch tall intake ports (!!). It also has some cool goodies, like machined rather than cast ports, etc..The intakes are specific as well, and are TALL! Look like a tunnel ram (which is true) and mostly dual quad. The medium riser came about by getting MOST of the good stuff from the hi-riser, but much easier to package in your Mom's Fairlane. The performance (even race) is about the same, which is why the medium riser is so much more common. Man! I didn't mean to carry on this way (sorry!).
