New, Old Stock is kind of a oxymoron term.. since when most folks think 'new' they think unused, in fresh condition.
New, Old Stock parts, especially ones that are 20 years old or better, are not often as nice as they were when they were, say.. less than 5 years old. You often hear phrases assoiciated with NOS parts, like:
'In great condition other than shelf wear'
'Item exhibits light surface rust'
'Sold as-is, no warranty.'
For the most part, if the NOS part you're looking at is all metal, and dosen't have any plastic, bakelite, leather, or rubber and has been kept in a dry, temperature controlled enviroment hermedically sealed in a containment vessle, then you might be alright.
No way i'd pay any money for 'New, Old Stock' tires, especially ones that are 20+ years old.. and I certianly wouldn't spend hundreds of hours and countless dollars restoring a truck just to slap ancient tires on it.. unless I was going to just park it in a museum some place.
I wouldn't buy NOS tubes, either.. at least, not the kind you put in tires! (NOS RCA Blackplate 6L6's are alright, tho!)
Other NOS things i'd probably avoid..
NOS Tolit Paper
NOS Medicine
NOS Dairy Products
NOS Gasoline
NOS Rubber Bands
NOS Fan Belts
You get the idea.
Some things just naturally break down over time, regardless if they've ever been used, or seen the outdoors at all.
Now, granted, tube tires are a little more sturdy than their tubeless bretheren.. some say that cracks and 'weather checking' on tires isn't a problem.. so long as chunks aren't falling off the tires.. but it sure isn't something i'd go tooling around town on.
The final thing to consider is, even if a tire looks alright, you never know whats going to happen to it when you slap it on a rim and start exerting force on it thru the installation, inflation, and normal driving process. I've seen relitavely new junkyard tires do that.. looked great till you slapped 'em on and put some air in 'em.. then they started looking like Liz Taylors face before facelift #3.
