Actually GM does. The Duramax is produced at the Moraine plant where the old 6.5 was built. It is produced by DMAX, a joint venture between GM and Izusu. DMAX is majority owned by GM since 2003. GM has all rights to the DMAX line worldwide. Isuzu actually builds a V6 Dmax used in Saabs and some other GM brands as well as Renault. Wish they would put it in a small PU. GM at one time owned 49% of Isuzu but now has no stake in the company. They continue to colaborate on design.
2004 Chevrolet 3500 LS D/A CC 4x4 LWB SRW
2007 Excel RT 30RKE