Fuel pump question

On a 1973 Cadillac fuel pump there are 2 outlets on the bottom. Can anyone tell me what the smaller one is used for? Can I just cap it off?

 

Im taking a guess , vacuum

73? humm might be feed back system?

 

The small line just runs the gas that the carb doesn't need back to the tank to keep the gas circulating and cool to prevent vapor lock. I'd run a line to the tank or find a pump without it.