I have an opportunity to buy some NOS front and rear nitrogen gas shocks for my 70 'Cuda at a reasonable price. Chrysler part number P4452127 & P4452124.
Seing that nitrogen gas shocks didn't become widely available until the early 80s, these aren't NOS as in 44 year old original equipment that came from the factory. The P prefix also means they were offered through the Direct Connection/Mopar Performance channels which again suggests they are not OEM installed. As a matter of fact, those exact part numbers are listed in the 2002 Performance Parts catalog. So these may be old stock shocks, but not in the sense you think they are.
If you are picking them up for like $5-10 each, and you have the original suspension under your car, they may be worth the risk, if the expansion retention straps are still on them. If they have been sitting topped out, I wouldn't mess with them.
FWIW, I seem to recall that the P number gas shocks were rebranded Gabriels. The P numbered race shocks were rebranded Carreras. So you can probably still pick up similar or even exact copies of these in nitrogen charged versions at your local parts store for $25 each. Use that to gauge the value of what a potentially 30 year old shock is worth.