The FE is pretty limited in the shorty style of header. You might look into the Sandersons. I see that Summit Racing carries them now. I’m not sure how they fit in a Cougar. They fit well in a buddy’s truck, but did require some massaging to get around the oil pan rail and windage tray – like they were built on a motor without either fitted to it. I don’t remember if they have a Mustang/Cougar specific model, but he was using the block-hugger style to fit the tighter chassis of an old F250.