What is this opening for?

pyrojim said
I think throttle rod, but this car has a throttle cable.
1966 dodge dart gt convertible.
Thanks

That's the traffic 'relief' portal - if you're stuck in traffic, you can take a leak out that hole. The Chevy and Ford version come with a hose that reaches up to the lap belt. The Mopar guys don't need the hose. ;-)