Confused on a new part from LMC (pics)

[KMK454]

I'm trying to put my truck to 100% stock so I picked up some 78 305 manifolds from LMC truck. I figured putting these on and just having an exhaust shop fabricate the rest of the piping and rebuild the carb would smooth out the motor and stop it from running so rich.

Well, here are the parts, and the left side manifolds are confusing me - what's up with the bolt? I can't find anything in Chilton's or in the engine bay that would bolt up to this part... anyone know?

Here is the pic:


Note the bolt on the bottom right... I'm thinking at this point of just plugging it up good if I can't see anything it's supposed to bolt to.