This is a link to Cobra Restorers who have the correct jigs for the FIA headers.
http://www.parts123.com/PartFrame.as...obra_Restorers
click on "model" Cobra and choose "Exhaust".
It's all about ROOM. The problem with the OEM FIA 289 drop type is that there is no room for getting any primary tube length and at the same time keep the mufflers under the doors, consequently the torque suffers significantly. Hence the reason for the redesign when the 427 came about. It is a lot of work to do otherwise, I have examples of what I ultimately did in my gallery, these are Dart Windsor Jr's.