On my 41 I used a Telflex cable or push pull cable if you will. I put a YJ wiper motor under the Dash and ran the cable up the A piller To the original wiper hardware that I had tied together with a small iron strap.
The Cable is secured to a plate that holds it so the back and forth action moves the wipers. The other end of the cable is secured to a plate that mounts the YJ motor. I used the YJ arm to provide the motion on that end. Best part is it didnt cost me any out of pocket money.Also hooked up the wiper delay switch using the original YJ stalk mounted hardware.

Sorry, I should have updated this.

I sold the truck after I installed a new transmission, without wipers. The guy I sold it to only drove the truck on nice days, so he never installed wipers. I saw the truck one time this past summer, the guy I sold it to has sold it, and I didn't see any wipers on it then either. To be honest, without fenders, and given the trucks traction problem, it would not had been fun to drive in rain.

Had I kept the truck, I probably would have went for the individual wiper motor & blade setup for each side. I may have tried to powered then through the same switch if I could have. A lot of things would have needed to have been changed if I kept the truck. Since I didn't fit in it well, selling it was the best option. I did get nearly all the money I spent to build it back, so it was gone, and the money was invested in my 49 Dodge 4x4.

The 1st pic is my 39 as I sold it. The rusty truck with the yellow door in the back ground is my 49, and the black Dakota (really bad frame) sitting next to it was the drive train donor truck for the 49. The 2nd pic is my 49 as it sits today. There is a build thread on it here.