My 89 GM 1 ton was tagged at 16K also. No issues carying the load once I put a set of helpers on it. The POS TH400 trans went out every 30K like clockwork, with 5K tranny oil changes. That was due to the tall first gear in it. Couldnt pull a 15% grade at 12K lbs. Yet the 81 GM C2500 with a 292 at 12K never stalled out into the mid 20% grade at 12K+ total! That ~6.8-1 first gear in the muncie trans helped!
My 92 IHC with a gross vehicle warranty rating of 18200 is tagged at 26K. Got pulled over at 27K.....no overweight ticket! I am good to just under 30K lbs per the WSP weight police. I was 10000 lbs per axel under the limit.
Marty