Identifying the connector for a ground connection

There’s a grounding post on the engine,

passenger’s side, between the fuel pump

and carburetor. It’s brass. It’s off.

The post has a hole in it; the mount to

which it was attached has a hole: it could

be threaded, but no screw I have fits: 4 is

too thick, 2 too thin; an odd one I have around screws in a bit but doesn’t hold. A

17-mm (or 21/32 inch) nut holds the mount

on, but I can’t budge it.

Neither my Haynes nor my Chilton’s identifies the connector.

Does anyone know what this is? It

runs without it.

'87 Toyota Pickup 22-R engine, carbureted