The 2" TTI that I have is the design from about 10 to 15 years ago. It was intended to fit an RB 440 with stock ports into an A body, and then also fit in a B body or E body since they are close to the engine. I first installed them on my low deck 400 in a 67 B body, and the only interference was the slight contact with the oil pan, and that was minimal. After many years in the B body, I moved the entire powertrain into the 75 A body, and that required the single tube to be modified to clear the pitman arm. I am certain there would have been no mods to that tube if I used an RB engine, or even raised port heads on my 400. Those TTIs have been really good for me. Not sure if they are still shaped the same in their current lineup.
