1 ton guys.... I need some help.

[Texasbigblock]

So on my 1969 dually (HO72) that I bought a little while back I have run into some problems. I went to replace the tires and rebuild the rear brakes and here is where the head scratching started.....
From my understanding, if original, the truck should have flat, 1/2'' lug nuts all the way around. My truck (Vidalia) has 9/16'' studs on the front (still drum brakes) and 9/16'' studs on the passenger rear but 1/2'' studs on the drivers rear.
Brake shoes and hardware kits for a '69 model fit in the rear and everything appeared to be the same as the stuff I took out. What is going on here?

Also, the 1/2'' studs on the drivers rear are tapered. I thought the original 1/2'' came flat on these trucks.
And the 9/16'' lugs are flat. I thought the later model 9/16'' duallys used tapered lugs and a retainer ring.

If I look for original lug nuts for this truck on Rock Auto, it calls for tapered 1/2'' lug nuts....
Any idea where to even start figuring out this mess?
Thanks