96 was a cross over year for GM, it could be OBD l or it could be OBD ll. If the port was never mounted by the coach builder it will be on the left side of the steering column. It may be loose, or it may still be zip tied on the main harness. The port it self may also have a cover over it. If you know you for sure have a 96 chassis it should be OBD ll. My buddy has a 96 Storm built on a 95 chassis, and it has a OBD l ecm and a OBD ll port, so it is a odd ball for sure.