According to my cornhead manual, Allis Chalmers made both a 330 and 338 black model. Each one was adjustable to 2 inches in either direction. The 330 could be set up as a 328, 330, or 332 and the 338 could be set up as a 336, 338, or 340. But as Tim(NJ) stated, I also have never seen a 338 on a K2. It may have only been offered as an F and G machine head since it contained more frame weight. Maybe It was only offered for a 1978 K2 and up, since they could have had torsion bar drive axles. Not sure. I need to do more reading.