The outer shackle straps on this 40 Pontiac are very long and sickle shaped. I'm sure they are from the factory since the rest of the car is unaltered. Just the outer on each side, not the inner. Some have guessed a jacking point but this would let the rear end drop a long way before raising the tire and, I have taken the left rear off using a floor jack so dropping for clearence isn't a reason. If someone comes up with the answer the prize will be the exact combination of cuss words to make a two piece AD headliner fit into place easily.
Evan, I couldn't find a picture of a '40 Pontiac, but I did find a good chasis picture of a '38. They are called jack pads. See attached illustration. http://www.oldcarbrochures.com/main.php?g2_itemId=69117 Ken
Re:Jack pads Yep,just talked to a guy today who knows these old Pontiacs,having hot rodded a few. He agrees that they are jacking points.
I drop to my knees and bow to you "Oh finding of the obscure on a computer Swami". I actually jacked it up by using this but it let the rear end drop a good ways before the tire cleared the floor. I guess they wanted to make sure the tire didn't hang on the fender when removing or installing. Thanks everyone.