1967 Firebird Question

First forgive the lack of knowleadge. I've got a 67 Firebird (326) question. There is some kind of relay (I think) that bolts to the firewall right below the voltage regulator. I assumed it was a starter relay, but seem to find that anywhere. It's a 2x2 metal casing with leads at the bottom. 2 screw on leads and 2 that have plugs and 1 that is a ground (aparently).

Reason I'm assuming this is my problem is that when I hook up the battery (no key in the ingition) this relay starts to whine. Car will still start, but the relay continues to make this whining/buzzing noise. Does anyone know what this is and where I can get one????

Any help would be appreciated and let me know what other information I can give.

SDA