Why settle for a second rate electric wiper when you already have the best one for an AD in place. The electric unit takes up valuable space ( you stated your truck is highly modified) which often means a-c and sound system in a very limited space under dash area. A 12v vacuum pump from a diesel will solve any wiper stop/stall problem and can be mounted anywhere. Instead of a single or two speed wiper you will have infinite number of speeds that will work pulling a heavy trailer up a steep hill. Your problem is with the vacuum source and not with the wiper motor.
