Alvin Kowalik has purchased many General Motors Co. pickup trucks over the years. But last year, the cattle rancher in Selma, Texas, tried something new, and purchased a pickup through GM’s Shop-Click-Drive website. “I found the truck, listed my trade-in and was given the sales price. A nice lady from the dealership calls me, we made a deal, they drove it out and I signed the papers,” Mr. Kowalik said.