Vacuum advance with two ports

[7991LXnSHO]

I helped tune up a 69 302 auto coupe that had two ports on the distributor’s vac advance. Which one should be hooked up to ported or manifold vacuum? And should the other be hooked up to a temp controlled, ported vacuum switch on the manifold?
A Diagram would help. Thanks!

 

[horseballz]

I believe one of those ports is actually vacuum "retard" but can't recall which one is which. Given our current fuel, I'm not sure that whole system is even valid any more, but I get the concept of wanting to make sure all is as it was originally! Carbs and their interaction with vacuum controlled distributors are tough in this day and age, as evidenced by another thread I've got going!
Just Sayin'
Gene

 

[7991LXnSHO]

Carbs are NBD compared to the learning curve of learning how to program an EFI.
Starting with a functional stock setup is the goal.