[Rick 427 Cobra]

Filler neck is always a good option. The higher the better to avoid spillage. Type of connection will depend on the neck construction, metal or rubber. Vent outside the trunk obviously.
If the tank is not installed horizontally, you may have to vent the high point of the tank or it will never fill completely. If this is the case, vent the tank to the filler neck and place an addional vent to the outside higher up on the neck.
Brass fitings can be soldered if you cannot weld. Its just plumbing!