My current truck is an early production '85 that used '84 emissions. Standards changed 1/1/85. I know CA HD trucks then had 2 smog pumps and the stainless exhaust manifolds. I remember seeing the tail pipes on half tons too. I always thought it was to slow down the pellets coming out of the pancake cats as they failed. Trucks are the only GM vehicles that had side exhaust at this height. I also remember the same tips on a friend's 79 or 80 C10 diesel. I can't recall if it had the screens or not. This was back in the late 80's. I figured they just used the same tail pipes in HD trucks due to cost.