Fuel System Help, PLEASE!

[72c20?c10]

I installed a ECE rear mount fuel tank in my 72 long bed.
The tank has a fuel pick up near the center of the tank and another fuel line connection in the front right corner. I called ECE and they said it was a vent.
I plumbed the tank using the stock aux tank fuel neck which has a built in vent tube (I think it is a vent tube) so I ran the vent line to it.
If I put the gas cap on is this a vent then? Where does it get it's venting?
I can't get gas to the carb.
I have an edelbrock electric fuel pump with an edelbrock fuel filter mounted on the crossmember near the tank. The fuel line runs to the rear of the engine up to the carb. Before the carb I have a glass fuel filter. Then the carb has a built in fuel filter. I heard you can't have too many fuel filters.
With the key on the pump pumps but no fuel gets to the carb.
Any suggestions. I will start a tear down diagnostic this evening.
I hope whomever reads this can stay awake to the end and help me.

ECE was no help. They are concerned with the tank only.

Thanks in advance.