I don't have the box, stock number or operators manual and could not find the answer when I Googled it.
Does the MTH Susquehanna #3638 diesel engine with Proto 2 run on 031 curves?
I doubt it because it's about 18 inches long, and the longest MTH diesel that I already have that barely navigates my 022 switches and does "the bump" when running through my 022 switches without derailing, is about 15 inches long.
Arnold