Transfer Case chain play?

Chain is not new. Truck has unknown mileage. It was a farm truck. Odometer got stuck at 69,000 miles. I am guessing 300,000 miles or more.
Thanks for the part number! Gears are old too, probably the same mileage.

Update. I bought a new chain, and the play was exactly the same. I installed it anyways and put the Xfer case back into the truck. It works perfectly. Unfortunately, it still leaks. I sealed it really good this time and let it sit for 3 days. Then I filled it with oil and let it sit for a few hours and then I installed it. I drove for about 10 minutes and as soon as I drove into my garage, I checked for leaks and sure enough, there was a quarter size drop on the floor within only a few minutes. Ugh. I can't get that case to seal. Now what? Take it out again, I guess.

Circled in red is a bolt that is not supposed to be there. I added it because the oil is leaking through the top inside of that hole (which I apparently did not put enough sealant on). So, I put a bolt in there and silicon around it and tightened it. I used Permatex ultra-light blue, which I think is wrong, it should be Permatex Black or Grey. What do you think?

Borge Warner 1354. I took it apart again and split the case and cleaned it all up and I Found al ittle tiny burr (only about.020 in.) Just above where it was leaking. So I smoothed it out and used black RTV and put the case halves back together and let the case sit inside for a couple of days now. This should stop the leak.