Back in 2003-04 when I was putting my 'Cuda together I wanted overdrive since I knew I would actually use the car, not just go to a handful of shows, cruises or autocrosses. Back then the Tremec TKO was the only real option. If I were doing it today, I would go with the Passion since it is a true bolt it. The Tremec did require a good deal of tunnel modification in order to get the driveline angles I wanted. On the plus side it has been trouble free and I've got around 50,000 miles on it now. I did break a spring in a McLeod clutch disc once, but the transmission itself hasn't given any trouble. I don't feel comfortable trying no lift, full on power shifts with it like I did with the 833 in my '63 Sport Fury, but I do shift quickly at 6,200 rpm without any problems. The biggest problems I see with it are tunnel fit in some models and the need for an external shift linkage in "E" bodies.