[realvc]

Hey Don, you're moving right along.

The big port next to the fill is a fill vent that runs up to the fill spout, one of the smaller ports might be a vent port to a canister and the other small port might be a return port. I've not seen your fuel sending unit but some times they have the fuel pick up tube and filter/screen/sock attached.
If you're using an in tank fuel pump and sending unit the vent and return may be built into that unit.

Good luck on sorting it all out, I know you can do it.
Take care.