Here is a picture from my '57 3600. The '59 would be the same. The little lug wrench that is about 8" long tucks behind the jack in the bracket and is held in place with the spring clamp. It is one of the L-shape ones with a lug socket on one end and a flat on the other to pry off the hubcaps.

http://s844.photobucket.com/user/ma...2751_zps1ae76f71.jpg.html?sort=3&o=1

It ironic thing about this assembly is that it would be absolutely worthless on a 3600 with either factory 17.5" or 19.5" rims unless you had a whole bunch of wood in the back of your truck to use as cribbing to get the jack up high enough to work. It is way too short to work from the ground all by itself. And good luck with the little lug wrench! You'd need a pretty good size hunk of pipe to use with it as a breaker bar. But, hey, it's original. Useless, but original. Probably why most got tossed!

I've bought replacement lug nuts at NAPA. Most of their stores have a cabinet with all kinds of different lug nuts. They are available in either long or stubby size. I get the longer ones because they fit my impact wrench better. Just bring one in and they'll match up to it. I'm pretty sure that they are 7/16-20 threads, but check to be sure. If you don't have one to bring in, just confirm the thread size and check with NAPA.

Matt