About 74-75 I had several 65-66 Mustangs with a couple being Fastbacks. My 66 got an engine transplant with a T-10 4-speed after the old engine and C-4 auto was used up but never did do anything about the 2.80 gears that the auto cars got. At the time, money wasn't exactly flowing out of my ears so it got a fresh set of Good Year recaps stuck on the front. My rear tires were pretty good but were a bit wider than the 'new' recaps were so they stayed on the back. My dad lived 150 miles away and the car was my main driver and it did that well once the new front end got installed. One day some guy when flying by me on I-10 about 1/3rd of the way to Lake Charles and so I shoved it into 3rd gear to try and catch up which I did but not before hitting 4800 on the tach....all it would do in 4th gear. About that time is when I remember the recaps lol. Figured if they were still holding together, they must be good and stayed behind him about 500 feet. Figured the mph with a 26" tire at 4800 to be just under 135.....and stayed around 4200 once I caught up with him. Didn't do that anymore, at least not with the recaps