[dsraven]

I know, old thread right? but if anybody is interested my 57 gmc has electric wipers from the factory. the firewall on these trucks may have a bigger bump to accommodate that motor. it could be made to fit with a bit of bodywork and is a stock part. not sure how easy to source, but stock none the less. there is a special switch also.
if adapting a newer wiper motor from something else try to get the switch and motor along with a section of the wiper actuating mechanism. that way you can use the original actuating parts that connect to the stock wiper shafts and use the newer parts welded onto those at the motor end. before removing the motor from the donor vehicle make sure the wipers are "parked" at the bottom of their stroke. then when you install and fab up brackets and arms etc as required ensure the wipers on the old truck are also parked. otherwise the wipers may work but they may park at some odd angle.

try delco remy number 5047909 for the original electric wiper motor