'68 Dodge Dart: Two openings in trans tunnel 4-speed manual

It's a boot for the console-automatic linkage. It isn't in the correct location and it's mounted on the 4-speed hump, which automatic cars do not have, so it obviously wasn't used for that. Who knows after 50+ years... anything can happen. It would be a totally stupid place to run tach wires, and the hole didn't need to be that big for wiring anyway, IMHO.