I'm in Arizona. I have a 1960 GMC. There are no honest junk yards here with old trucks. I can try and find you the part you need if you get me a picture of the other side piece. Your GMC came with rear leaf springs with a Dana 44. Chevy had trailing arm/coil rear.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn