I'm doing my first porting job on a set of D0OE/351 heads. I have two quarstions

1. What is the second exhaust passage exiting the second cylinder of each head? It looks like it goes to the intake side of the manifold. I'm not sure what I should do with it with respect to porting.
2. I want to install 1.94/1.60 valves but an not sure what to buy. Some speed catalogues list 1.94/1.60 in the Chevy section and also under the Ford section with a note that the valves are .050 longer. Should I just but the standard length Chevy valves? I'm planning on using roller tip rail type rocker arms.

I'd appreciate any words of experience on this thanks.