cruise vacuum servo????

[srs244]

i have a 78 pace car L-48, auto. i do not have any of the original documentation on my car. i'm in the process of putting it back into original condition after it has been "bubba-tized" at some point during it's lifetime.

my question is this:
there is a vacuum pot mounted near the firewall in the engine compartment, on the driver's side, to the engine side of the brake booster/master cylinder that looks very much like the ones i have seen for auction (and in my assembly manual) for a cruise control option. i DO NOT have a cruise/turn signal "stalk" on the steering column. there also doesn't appear to be any type of servo as indicated by the assembly manual below the brake booster, etc. this vacuum pot is not connected at this time to anything. it has neither the assembly that should connect to the accelerator portion of the carb or any vacuum hose connected to the back of it. here is an additional fact that has me completely confused. i have a local friend who just bought a 78 L-48 in pretty much original condition from a third owner. HE DOES NOT HAVE CRUISE on this vehicle, but has the same vacuum pot and assembly connected to the carb. no cruise servo, no brake cut-off switch, but the same vacuum device indicated in the assembly manual as part of the cruise control system.

can someone tell me exactly what this is and what it's function is on a non cruise system car?? additionally can you tell me what the portion that connects to the carb is called (part numbers would be greatly appreciated!!) and where it gets vacuum FROM.

many thanks for the assistance.

steve