If the owner formerly ever had a 22R series truck, he might be hearing ticking or rattling that indicates to him in his mind that the 80 needs a new timing chain, based on his prior experience, but as mentioned before, the timing chain system on the 1FZ is MUCH better designed than on the later model 22Rs and doesn't usually fail. Especially not at lower mileages.
However, if there's noise, it could be another problem. We'll have to hear more details on how he came to the conclusion. Make sure this isn't a mileage roll back also...do a carfax at the very least.
If the engine is not runnable at all...then it may not be worth it, regardless of the mileage. If you don't do your own work, you'll be looking at many thousands of dollars to do much of anything major to a 1FZ, whether it be a headgasket change or a whole new motor.
However, as far as timing chain failure...stranger things have happened. There's a poor guy on mud that had his 1FZ oil pump drive gear fail, which is exceedingly rare and to make matters worse, this is the one part that cannot be replaced and usually means the block is junk, so he's had to get a whole new engine.