Just wanted to share. I'm in the middle of my 2100 swap. I have 4 carbs that I got, I've got one rebuilt and am planning on the selling a second rebuilt one to cover costs eventually.
This weekend I pulled my carter off to fit up the adapter I got from summit and it didn't fit, stud space was too narrow on the 1bbl side. I called Summit this morning and they are shipping me the one that has the right spacing, great service.
Here are the part #'s for the adapter.
Right one: TRD-2041 - 2 15/16" stud space
Wrong: TRD-2044 - 2 5/8" stud space
Also, I read this somewhere and can validate, be aware that the later 2100's have a gap in the bottom plate that won't fit on these adapters, you need an earlier model 2100 that has a solid base on the back (opposite bowl side).