According too Ohio George, he started out adapting his hydro-Stick transmission to the SOHC. THE problem was the Willys was a real handful with the SOHC ,engine, so Ford's Charlie Gray told him they would build a C6, so he could keep both hands on the steering wheel. He used a C6 after that in the Willys and the Mustang. George said it shifted gears at over 8000rpm, and was reliable. I believe Gas Ronda's Mustang also had a C6 behind the SOHC.
George was a good talk at the Fe reunions, and he told me the Mustang was like driving a Rolls Royce, down the track compared to the Willys. The Willys is in the Henry Ford museum collection.