Em, I can't find whether you said it's a 3 or 4 speed currently. Perhaps, you can sell him on the merits of a cool T-5 with a hydraulic clutch. I think it's a pretty easy swap on these cars and would be cooler than the automatic for sure!

Although, I must confess, I had a '66 Mustang coupe back in the 80s. It was a 289/auto. The auto trans started slipping. My dad had the pedals, clutch & 4sp tranny from a '65 Mustang he had parted out so we decided to swap it in. The result was I kinda hated it because the clutch was really stiff, the trans didn't really shift smooth or quick, and it was a pain as my daily driver. So I got the auto trans rebuilt and stuck it back in there. Now, if it has shifted as easily and smooth as these more modern sticks, I would have loved it! Just sayin....