The original Blackstone in my '93 only died last year. I don't expect the replacement to last as long, but 8 years seems a bit on the short side.

Also, I would trust the cheapest brand new radiator available over an old used one, even pressure tested. I recently replaced my heater core and could not find the leak on the old one. I pressurized it to 20psi and still no leak. Fearing I may have been wrong, I finally flushed the core with the garden hose and repressurized to just over 15psi before finally seeing bubbles (in a bucket of water). Some little bit of debris, I guess, had hidden the leak.

You don't know what a used radiator looks like inside, and I suspect that after buying a used one and paying a shop to check it out, you would not be saving enough money for all that hassle.