The new turbo pump just arrived. The Turbopump itself has has a 4.5″ conflat flange for an inlet. Attached to the turbopump inlet is a 4.5″ to 2.75″ reducer.
I think as a first step, I’m going to skip the heroics of putting the chamber on it’s side, and just buy a 2.75″ 90˚ conflat elbow. Cheap and easy to install. I realize this is not an optimal connection for the pump (skinny with a bend). But ultimately I have time, and if it takes days to get down to vacuum… so be it.