I put an aftermarket motor + switch etc in my 58 and it works fine. Although I live in Calif and mostly don't drive it much in the rain, but the times I have it works great. Of course the kit doesn't come with the "connecting rods? (whatever they're called) that attach to the wiper motor and connect to the wipers themselves-So you'd still need that stuff. and suppose maybe you have that.

I looked through my build notes and don't see the the actual paperwork but it appears the same as the one in the current Sacramento Vintage Ford Book p/n 8192-1 1956-60 $175.

Just another option.