Look for a unit history of the 601st TD battalion. That was one of the few which saw much combat in Tunisia, it was there from November 1942, and was equipped originally with the GMC TD. And, if my memory serves those did shoot at Axis tanks. They may have been involved in a company size action vs a German armor column near Medjeb al Bab in December 1942. I'll have to dig some books out and search.