Is this a radiator leak 80 el camino 305?? Pictures inside?

What the arrow points to is simply a vacuum piece, it should have no coolant involved if it is leaking. Just behind that part the heater core line connection, the screw looking piece with a 5/8 rubber line connected, will leak coolant with a pion- and it may be spraying. There are two possibilities- the hose is bad and spraying on the vacuum can, making it look like it is leaking, or the sealing material around the plug is hard and leaking, again spraying on the vacuum can.