Can it be changed?

I'm not sure if this where I need to ask this but here it goes. I have a 68 barracuda and I needed a wiper linkage assembly. So I bought an assembly in carlisle not thinking about if it was for a two or three speed set up. Turns out, it was for a three speed wiper set up. So...my question is can a two speed wiper set up be converted to a three speed wiper set up? Has anyone ever done this and if so, what did you have to do? Thank you for your help.