To start with I believe you have the wrong thermostat housing.
look at this one from summit: 1966 DODGE DART Dorman Thermostat Housings 902-3022
Then you upper hose will be gates 20416 and lower will be 20386
Try a local OReilly...
The thermostat housing in the engine picture is correct for non A/C 273's. The Summit Dorman picture housing is for 273 engines w A/C. Nibble is canted toward driver side for compressor clearance.
You already have the correct housing.
