The shoes should be easy, since the standard Bendix design used on most cars. You just need to know the (missing) drum diameter and the shoe width. I think to rebuild the wheel cylinders all you need to know is the bore, though new cylinders are almost as cheap as a kit. Check PN's on rockauto and they probably just map to the cylinder bore. You have the later style self-adjusters. If you buy a "brake hardware kit" you get new ones and springs for ~$7/axle. As for the shoes, you need to know the diameter and width.
The drum may be trickier to figure. It isn't just the shoe width since some Mopars had bell-shaped drums that had a narrower width where the shoe acts. Another way to say this is that the wheel hub surface stuck out way past the shoes. We can't tell without a side view of your brakes & hub. Also measure the wheel centering hole that should match the thru hole in the drum center. Centric is good about giving almost all the dimensions of their drums, which will help. Check rockauto.
