When I checked the slack in Bazza's 318 last summer I ran across a little tidbit of information (here or elsewhere, I don't recall) that said that if there was 5* of "slop" between the timing marks when you rotate it backwards and forwards, it's worn-out. Not sure if that was "By the Book", but I followed it.
And I took a video of this for Bazza as well:
Another way of thinking about this: If there's slack in that chain, how accurate is your timing going to be, and thus, how well is your engine going to run?
Of course you could always just say, "Screw it! I'm already in here, and I may as well take care of it", which is what I would do.
I worked with a mechanic who would not do a tuneup on an engine with 30k+ miles on the timing set. A bit excessive IMHO, but that was linkbelt chains and nylon cam gears. His claim was you can never get the engine to run properly. I turn the engine back and forth to get an idea of the chain slop. Just do not get carried away and turn the cam. Getting rid of the nylon gear is a good idea. Replace with a reputable true roller set.
A block that has been align honed may need a timing set to compensate, that is designed to take up the shorter cam to crank centerline distance.
With the low mileage and the slop is not bad, I would run it. When running, check timing deviation/scatter with the timing light. A couple of degrees will not hurt how the engine runs or power. A hi perf or race engine is a different conversation.