Need help with drum brakes

So backed the hay monster out of the barn the other day, and as it started moving, heard a big BANG out of the back axle. 

Got it moved where it needed to  be, then found rear axle locked up. Jacked it up and what we found was left rear tires were locked up. Once we pulled it all apart, what we found was a broken retractor spring on the brake drum pads.  No worries, we just get a spring kit. 

Not so fast........what spring kit? Truck parts place spent half an hour looking and came to conclusion it would need a Leland K196 kit. This one........

Except the springs in place, and busted one don't match up to the picture.

So in order to try to narrow this down, how does one go about knowing what axle, what brakes and brake drum kit I actually need? Are there any ID numbers to be found anywhere? 

Believe hay monster was built on a Dodge D600 truck chassis, circa 1970, but that is a ballpark year only. Also believe rear axle is same one it left factory with, but no way of knowing for certain. 

So spring went on and looked to be a good fit. Except when mounted, brake drum was still locked up. Took it all back off and eventually took off both return springs and left brake pad. Aside from the broken spring (which had clearly been broken a long time), the fault seems to have been the self adjuster, which was locked up. Took all that off and got it freed up......all eventually back on........a guy needs as many hands and arms as an octopus......and brake drum would now turn freely.  As it stands now, all back together. 

Test will be tomorrow when I fire it up to return back to the barn. If brakes work, victory will be declared. 

That being said, the new DISC brakes are great...  If your not getting 50K miles on a set, you doing something wrong... We have a 2019 Ford Flex with ceramic discs.. 68,000 miles and i am going to do the rear brakes this week... Front are ORIGINAL and still plenty of material left... Some guys are getting 100K on these discs..

Now that you mention it, problem with brakes started as  I was backing out of barn. As soon as it started moving, there was a loud BANG back there......buy guess is that was when it let go after who knows how long that spring had been broken. BTW, that may have been 2nd break. Spring looked to have been broken and welded once before. 

So even more fun........this was on left side and lug nuts on that side are left hand thread. Unless you knew that, you were in for a fight getting wheels off. Some are left hand thread, some right hand and some are a mix of both. 

Some engineer somewhere should have been required to have had a very good reason for all that, or just hang em. 

As for Disc brakes: any single vehicle that I've had to deal with that had them (weather it be a small car, pick up or tractor trailer) was more of a PIA for maintenance and repair than all of the vehicles with drum brakes combined I've owned over the last 50+ years. Once I get my newest acquisition up and running I'll be looking to sell the 1989 Dodge/Cummins which is the only thing I currently own with disc brakes. They work fine when it's driven often, but if it sits a spell it needs calaipers. Never needs rotors or pads, just the pistons seize up from lack of use. None of my drum brake vehicles have a problem sitting for long periods. And the disc brakes I've had experience with on large trucks have been dangerous. One Gasoline tanker I drove had so many problems that the axles were removed and replaced with drum brake axles.