OK, so maybe I am not asking that correctly. So, let me explain...

I have done this before but it was a long time ago and I don't remember how I did it.

This piece will be cast in aluminum. Therefore, I am having to design with mold making in mind. The top piece was created using a thin loft. The end of the loft sits on my top plane:

The base had to be designed with loft from the center out. Now I want to take the end of my loft and extrude it down to meet the top of the base. I believe there used to be a command that would just let me grad the "surface" and tell it to "connect" to the other surface (not to be confused with surfacing tools - I am talking about extending the boss to the base)...

How did I do this before? OR...how can I do it now?