I went out to the warehouse and pulled the 6 and 7-Way Trailer Connector Mounting Box, # 18159, and the 4 Pole to 7 Pole and 4 Pole Adapter, # 37185, and test fit them to be sure, and the mounting holes line up perfectly.
You will need longer screws to go through the housing on the # 37185 adapter, and the sides of the adapter will hang over the edges of the # 18159 mounting box 1/8 inch on the two sides. view full answer...