Where is the neutral switch on a 1965 Chevy Impala?

A 1965 Chevy Impala doesn't have a "neutral switch" in the same way a modern automatic transmission might. Instead, the equivalent function is performed by the neutral safety switch, also sometimes called a starting safety switch. This switch is integrated into the steering column, near the ignition switch and the gear selector itself. It's not a separate, easily identifiable switch. It's a component within the steering column assembly.