The back side of the TRam is flat all the way up to the bolt on top. It is exactly 2 1/4" from the center of the dizzy hole to the back edge of the TRam. 4 1/2" might just make it if there are no clips sticking out.... No need for vacuum adv. So that shouldnt be an issue. Thanks guys really appreciate the help here. If we get some different measurements in might be a good thing to list the sizes here for different makes and models for future reference. I cant find any measurements on line so short of actually calling the MFG. and asking them to measure them we are out of luck. With tight fire walls and other clearence issues this might be good info. to have stored somewhere where it can be quickly found?