The KMC Z-72 was the best of that bunch of older style KMC chains, with outer plates shaped for crisp shifting, mushroom head rivets, a Missing Link, and good wear qualities for an inexpensive chain. I usually bought 'em via Amazon for around $7 each, and still have a few. No problems with my various 7-speed setups, using Suntour and Shimano groups, freewheels and cassettes.

That particular chain worked best for me with index shifting. The shaped plates could be a bit fiddly with friction shifting and I found myself fine tuning the levers more often than with the cheaper Z51 and similar chains with flat plates and plain rivets, particularly with Suntour Alpha freewheels. Not sure why. I've switched to all SunRace freewheels because they shift and run better (but only the MFR-30 and MFM-30 chromed 7-speed; not all SunRace freewheels are made as well).

I noticed KMC revamped its lineup, mostly renaming some existing chains, but also apparently phasing out others. So I've stocked up on a few Shimano and SRAM chains to try, since REI was blowing out some parts cheaply this summer. Good time to stock up on older style drivetrain bits because the pandemic is disrupting the supply chain and some stores may not restock these anytime soon.