The 5.0 HO used a double-roller timing chain. A lot can get a couple hundred thousand miles out of them with no problems. If you start having inaccurate ignition timing and are having problems with power (when compression and leakdown testing test fine), the only way to check is to get at it. Most will say using a dial indicator, .50" of deflection is about the service limit if you want the nitty-gritty.
I agree, the engine will often wear out before the timing chain is an issue. At the same time, if you ever do cam change or have the timing cover off, its not a bad idea to replace it anyway.
I wouldn't worry about it unless you change cams or the car runs ragged due to chain stretch(not likely). The double roller chain has no plastic parts like your Buick so it will last as long as the motor itself.
If you put a socket on the crankshaft pulley/damper bolt and turn the crank a little back and forth you can feel the timing chain play by hand and it kind of gives you a ballpark feel of how tight/sloppy it is.
I forget now,but I recall from the past that if it was more than "X" degrees play on the timing marks,a new chain was in order.
But like someone stated,the 5.0L roller chains last a long time.I checked the play in mine at just over 100,000 miles moving the crank by hand each way and it felt extremely tight,with just very slight play when turning right and left on the crank.
there is no play at the crank at all, i replaced the balancer last night and was just wondering about the chain since i was pretty much halfway there....guess ill leve it alone for now thanks