Carter AVS info needed

The jets and metering rods are in the carb; its an unopened unit that just needs rebuilding.
I think he just wants to be sure the correct sized ones are in there to be sure nobody changed them out over the years, or to see if they're worn too much.
He knows it's a stone stock 340/727.

There is a big threaded plug in the top of the carb. Is that supposed to be there??

George