Edelbrock LD4B ?s

I have an Edelbroack LD4B intake manifold I got off of E-Bay that I have a few questions about (please see photo).

#1 What is the hole in the rear of the manifold (between the Chrysler part number and the edelbrock "E") used for? Do I need it? If not, what should I "plug" it with? Would teflon tape on a pipe plug be enough? Will a pipe plug restrict fuel flow? Should I worry about the flow?

#2 I have an Edelbrock 1406 carburetor (currently on my buddy's truck so I can't measure it) to put on this manifold. Does the 1406 mount using the studs currently on the manifold, or will I need to move the studs to the inside holes?

#3 What size (length) are the thermostat housing mounting bolts? I have a couple of bolts that thread in about 3 full turns. Is that enough? If not, should I run a tap/die through the holes?

Thanks for any input & I'm sure I'll have more ?s