New Guy, 72 Plymouth Duster, where to start looking?

First thing I would do is a full brake job as that could reveal a scraping noise such as thrown pad lining, broken spring flopping around in the drum, or even the hubs actual cap having fallen off the hub and rattling around in the wheel hubcap.

Second, check suspension bushings and ball joints etc for slop and replace as necessary. Even in same family it’s a 50 year old car that has been sitting and rubber bushings hate that.

As for oil and temp, do yourself a favor and for now, bypass factory gauges and add in mechanical gauges til you get a feel for the actual conditions. In my 1972 Duster I run a mechanical oil pressure gauge, actual voltage gauge and bypassed the ammeter and oil light since sending unit was gone. On my Duster it is a 340 and can take what seems like forever to get up to temperature. I have a 180 thermostat in in and the first line of the normal range is where my needle is when the thermostat opens, and it only goes up when heat soaking when turning off engine. Something to look at is grounds, a lot can be screwy on the gauges if there is not a proper ground path.

It sounds like you are off to a good start at least. Welcome to FABO.