if its a married 205 from an auto truck then it will be 23 spline. in that case, to swap a 32 spline input in the 205 you have to have the case machined to accept the larger input shaft bearing. not a really difficult thing to do, just time consuming and annoying. if you can find a GM 205 from a th400 truck it will have the 32 spline input. also dodge 29 spline 205s that where used behind the getrag 5 speed have the large bearing bore that accepts the 32 spline input and bearing without needing machine work.

my concern is that when you turn the 203 range box around to use it as an overdrive you will need a male input on your 205, so the two mesh. i don't know much about dodge 203s, but i know that the GM 203 from behind a TH350 will have a female 27 spline input, and the GM 205s from a TH350 will have a male 27 spline input. if you don't find a combination liek that you will have to have a custome spud shaft made.

ryan