2speed to 3speed wiper changeover

there is quite a bit of difference-- also the vari motor is year specific--- 67-68 differs from late 68 to early 70 -- then they are more standard after that (3speed). I think you can use any of them-- if you know how to clock them-- but I'm not sure-- this seems to be witch craft on this subject .

the transmissions are different in 67 & 68 they use a different type bushing vs 69 which uses a plastic item, I do not know if the arms are the same-- Lawrence