jul 16, 2021 · this chevy truck generation was officially designated gmt400, but some enthusiasts refer to it as obs, short for old body style. That all changed when the gmt800 arrived on the scene for. sep 7, 2021 · learn about the major differences and changes in chevy trucks from 1988 to 1998, also known as the obs (original body style) era. See the highlights of design, performance, comfort and safety features of the gmt400 series.
