Mine has the 3-way part, with the 3 hoses in and 1 out, but it is smaller and works as a fume collector (and assumed liquid separator).

Maybe he has a sealed replacement cap when a vented cap was original on his configuration?

Any spider that came with an evap emissions system did not come with a vented gas cap and they also have a 3 to 1 fume collector in the trunk.

The schematic for the carb'd version of the evap emissions system is quite a bit different than the one for the fi cars.

The fi cars have that check valve underneath the car and no 3 way valve in the trunk. The carb'd cars have the 3 way valve in the trunk with no check valve underneath the car.

Make up air in a carb'd car is pulled from a small orifice built into the body of the 3 way valve. Make up air for fi cars is pulled from the charcoal cannister.

Can anyone explain why there would be 3 hoses coming from the tank merging into one hose (see RRoller's diagram and my photo at top of thread)?

Probably to provide enough volume for the fumes to condense into a drop and flow back down into the tank? It only makes sense if it has something to do with a minimum necessary volume in that section of the line, as there is no anti-tip-over leak valve or anything like that there.