I bought three rear wiper arms for a 1998-2007 Chevrolet Venture. They're about 12 inches long. I bent the ends about 10 degrees using my heat gun and vise. The 15 inch wiper blades fit well. I need to move the center pivot up about 5/8 inch, but they look pretty good otherwise.
I moved the connecting rod pivot point on the middle arm and got the three arms moving about the same arc from rest to full up. Finally. Now to locate two more 12 inch arms (rear wiper for a Chevrolet Venture). The one I have is on the left in the photos.
The windshield wipers are getting close to completion after moving the wiper motor mount 1/2 inch lower. I had to rework the mount points for the pivots as the wiper arm ends were past the horizontal center line of the windshield. I fabricated a couple of brackets from sheet metal, flanged the edges with a hammer and dolly, and curved them a bit with the shrinker. Now, 12 inch wiper arms place the wiper blades properly on the glass. The driver's arm has too much travel, so I'll rework the connection rod's mount points on the center pivot.
I've been working on the wiper motor mount. I retained the mounting point for the S10 and recreated the bracket using those points as the basis. It's welded in to the new trough, but the bracket places the motor about a quarter inch too high. I'll have to reposition it.
The trough for the wiper assembly came together today. It has a flange along the top to weld beneath the windshield frame and an arched bottom that tilts down toward the cab and to the sides. It will all be seam-sealed to (hopefully) be watertight.
This move to replace the firewall will have two benefits: legroom and space for a Vintage Air system. A/C is a requirement during a Houston, Texas summer.