I am going to be building a motor at some point and I am still debating on the tranny also. Obviously I am going to be needing a strong tranny. I am hoping for low 12 on the motor and maybe mid to low 11s on nitrous. However, I may only hit the track twice a month if that. The car will be daily driven and being able to take the car for a decent ride somewhere (like over an hour or two) on the highway would be a nice benefit. However, the 700s are expensive to build up vs. the old Turbo 350s and 400s, so I started looking into those and was suprised at just how much cheaper you can build them to hold more numbers. What are the main differences between the TH350 and TH400? For my application: which of the two would you go with and what gearing would you recommend, or would you recommend keeping the OD tranny and getting 3.73s?