If I recall correctly, this is a little core plug installed from the factory, and isn't meant to be removed.
You can seal it with J-B Weld (not J-B Kwik), by removing carburetor, cleaning and filling the plug with the cold weld.
When fully cured (24 hours), J-B Weld is completely resistant to water, gasoline and about every other petroleum product or automotive chemical (temperature resistant from -67° to 500° continuous, 600° intermittent - LINK).
May God's grace bless you in the Lord Jesus Christ.
'92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.