1953 chevy 3 dueces help

hello I need some help or advice I just purchased a rebuilt 54 chevy 6 poper bored 30 over and fixed up but im comfused it has the fenton headers and the 3 dueces
my question is in the picture there are one hole in each of the headers on the bottom
my second question is on the 3 dueces the center has the opening on the bottom like the original intake that hooks up to the original intake
But with the headers and 3 dueces where or what up up in the middle square piece

 

You can run the heat from there to the bottom of the intake in order to heat up the manifold.