I cannot remember a tranny with that shift pattern but I must have run across it in my days,I have for sure seen reverse in that slot but not sure if it was a 5 speed or not.I don't ever remember an R-185 model,they went from R-180 to R-190 I thought and it seems like the "R" series was 1956.I used to know the prefix for the other years too but that was a long time ago.The cab style changed in the upsizing from 180 to 190 and now I learn that there was an 185 in the mix so learned something today.That could have been their designation for a custom application like the fire truck.The engine would have been a straight OHV six.I have ridden a lot of miles in those truck as a passenger hauling pulpwood and logs before I could even drive.Ron G