It can be checked for stretch
There are offset woodruf keys to adjust timing. I think they go to 10 degrees. After that, replace the chain.
THere is no official life of a timing chain but the guides are plastic and, especially if overheated, can break and jam between the chain and sprocket. This will cause the chain to jump and when the motor is out of time, pistons and valves will try to share the same space. The motor will then need a complete rebuild that will run in the $6000 range.
Some mechanics on this site recommend 120,000 intervals for the chain, rails and tensioner. I did mine at 100,000 because I fear that the old owner didn't maintain it. It was a precaution.