This?
View attachment 1715580124
It looks like a horn relay, but more often that's on the left cowl.
And yes its an electromechanical solenoid relay. Just so you know, in automotive speak usually 'solenoid' is reserved for the one that actuates the starter engagement.
A '72 Dodge Chassis or Plymough Service manual
may have a connector identification table.
This snip is from '73 Dodge as an example of one that does.
View attachment 1715580119
CI = Connector Instrument Panel
The first letter-number on a wire is the circuit and wire section. M appears to be Map. A is battery, R is alternator, J is run & ignition. Q is accessory power. S is start
Next group on the wire label is SAE wire gage followed by color. 20P is 20 ga Pink. 20BR/Y* is 20 gage Brown with Yellow trace (stripe)
If you have decent internet and a computer, mymopar.com has free scans of many service manuals in the 'reference' subsection. IIRC there is a '72 in there.
They also have seperate electrical diagrams, but those are non-factory and generally not as accurate or complete.
