You need to be careful with the age of these tires. BFG's and Pirelli's start to crack through the outer treads somewhere around three years of age.
The BFG's in particular will throw chunks of tread out like the retreads used to, leaving you to look at just the fiber from the carcass.
The Pirelli's crack like this too between the tread blocks.
One of the memebers here in Europe bought a Pirelli tire like this, NOS, and it failed within 30 or 40 miles.
This considered, what is the point in looking for NOS tires that are more then a year old from manufacture regardless of whether or not they are used or not?
Try the Mickey Thompson LT rear tires. There are more then a few 225-vr50-15 tires still made.
You just are not going to find a matching set, front-back, in 15".
Even Hoosier no longer makes them.