PYPES SGF 70 . Look for/at its transverse crossflow. We got to help design and test the system. It works and sounds great and is not too loud or quiet, has no drone and flows terrifically. 2.5" mandrel bent BUT it will take some fitting.
Did it long ago for a early 70s Firebird and just put it on a 74 455 powered GTO/Ventura.
Tom