I've had the Tremec in since late '03 or early '04. At the time it was the only real option. The 1st. transmission they sent me was an early one and it wouldn't fit worth a d#$%. They sent me an updated version at their expense and it fit a lot better, but I still needed to work the tunnel over to get the driveline angle I wanted. I agree Tremecs tend to be notchy and the earlier trans like mine have more 1 st. gear reduction than is either wanted or needed. The TKO definitely shifts better than the T-5 in my daily driver Mustang, but I still don't trust it for full throtle power shifts. On that subject if you make a habit of full throtle power shifts you are going to eventually have sychro problems unless it is a true racing transmission. Still the TKO can be shifted pretty quickly, just a momentary throtle lift. The T 56 may shift better [ I haven't driven one ], but it is a lot bigger and heavier and the only reason they have double overdrive is to help the OEM's make C A F E standards. Most fair size engines have a broad enough torque curve that they don't really need more than five speeds. As for the Passion unit, I've met Jamie and seen the prototype transmission at the Indy trade show a year ago. IMO he is determined to produce a quality product and it looks to me like it will fit without any significant chassis modifications. The only real question is when will it be ready? As for cost, the Tremec transmission itself is cheaper, but when you add in the cost of everything else needed to make it work it should come out about the same. Finally there is the Keisler SS 700. Currently this transmission isn't available for "E" bodies, but they are working on it. I was in Knoxville back in April and I took the opportunity to stop in [ unannounced ] and see their operation first hand. They gave me a tour of the place and they are actually assembling transmissions. The SS 700 appears to be an easier fit than the Tremec, but I can't be sure of this. Good luck with your project. Pm me if you wish and I'll give you contact info if you want to talk about this in greater detail.