I do not think they all had units installed with the air cleaner inlet cut into the support.
Think I have some 1960's pictures, Shelby, where they simply turned the air cleaner down and ran horizontal with the support towards the frame. Fit well.
Either way, there are only a few tricks one can do for the WOW factor and performance, Webers, Dual fours, supercharges, Hillborn , there are a few others I think.
Like gt350R said, be selective with holes.