what part am i missing to connect the cable to the integral switch on the wiper motor?
That wiper motor is missing the piece that slides along that rectangular channel. The wiper control cables end is supposed to fit into a slot of the slider piece. Assuming that this is a Trico wiper motor from 55-57 Chevy?
The plastic, switch, slider piece is reproduced for the Delco wiper motor.
An idea where to source one?
A quick Google search...not an endorsement...I'm sure there are others.
https://fpautoparts.com/Interior/1957-Chevrolet-Full-Size-Cars/Corvette-Wiper-Switch-Actuator-Assembly-Each-5156?msclkid=1a00318f89e61463ba13567c90d594fa&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping%20-%20Trim%20Parts&utm_term=4588193306160935&utm_content=Price%20Ranges
Thank you to all the responders. You were a great help