1979 dodge aspen replacement fuel tank

[Dylan Bobek]

Why is there an extra hole on the new fuel tank does any one know what it’s for

 

[80mirada]

vent valve goes there on 80 and up cars.

 

[Aspen500]

Yes, it is for the rollover vent valve. Also used on '79 built after May something (like my '79). Not sure how you would block the hole off for use on earlier cars.