No clue what those are ha, but shot in the dark, probably looking a little rusty ha
Look under the back of the car. On either side of the gas tank will be a box-section steel framerail welded onto the floorpan. Your rear leaf springs will connect to these framerails with shackles.
This is what they look like with the trunk floor removed. The rear crossmember is the section joining the two framerails closest to the camera:
This is the RH framerail (without the crossmember welded in):
And this is what you don't want to find at all - the framerail rotted through with the rear of the car supported entirely by the trunk floor. If you have this, you'll need to weld in a replacement frame rail before driving the car:
Also look at your trunk floor. With the rot you have on the quarters, it is highly possible that both the trunk floor and the gas tank hanger strap (the crossbar closer to the differential in the photo below, just above the rear sway bar - also seen hanging from the LH side of the frame the first photo I posted) are rotting. Last thing you need is for your gas tank to drop on you while driving.
-Kurt