Need help from the 60-66 Experts...

[REDNOSE65]

I bought my 65 Chevy Step Side in about 1996. The previous owner didn't do anything to it and the person he bought the truck from is long and gone. He did all kinds of stuff to the truck, but did more harm than good meaning more work to make it right. Any how, to start with it has leaf springs in the rear. I don't think that's original, is it? The cab mounts align perfect. The rear is a different story. The bed doesn't align so much. I tried installing the rear bumper, but the brackets don't align at all. Can anyone tell me what years used leaf springs? 60-61??? Any info will be greatly appreciated. Here are some pics to I hope explian what I'm talking about.