Need help..stock '74 engine compartment pics.

66 CUDA said
That is the horn relay.

No, no, nothing to do with the horn! That is the seat belt interlock relay unique to 1974 Mopars. Here is a link to check out;

Seat Belt Interlock system - Moparchat - Home of MOPAR enthusiasts worldwide!

Most folks defeated them, Google to find out how....