My new header tank is here! Ok, now what the heck is this part for?

My replacement aluminum header tank has a couple extra holes that my poly tank did not have. I've figured out all that, but two parts have me puzzled. What is the 3" piece of 1-1/4" radiator hose and flange adapter for? My first guess is for the new sump drain, but my tank is nowhere near the bottom fabric where the 3" hose would reach. And I guess the alum flange would glue to the fabric?