You've provided links to your own website. No surprise that you agree with yourself.

But if I have to pick someone that is wrong, it's not Sheldon Brown. He, along with every other source you care to look at, will tell you that 6, 7, and 8 speed chains are the same, and that's true for Shimano, KMC, and SRAM.

Like the OP, I have a 1985 Ironman (now on loan to my son) but I left it 6 speed. Guess which chain I used? Shimano HG71, which is a 6, 7, and 8 speed chain. My 1987 Fuji Del Rey is also a 6 speed. Same chain, the Shimano HG71. My Trek 750 and Specialized Sirrus are 8 speed - same chain. My MTBs are all 7 speed - same chain.

In fact all 14 of my bikes are 6, 7, or 8 speed. They all use the same chain and a Shimano HG71 is my standard. I keep one spare chain and know that it will fit all of my bikes. I'm not even sure I could buy something that says it's a "6 speed" chain. They typically advertise them as 8 speed, but they also fit 6 and 7 speed and most of them say that right on the packaging.

This is a ridiculous discussion that will do nothing to help anyone coming into this thread later on. The OP already knows he can use 6-7-8 speed chains on his bike, and anyone reading this in the future will just Google it and discover the same.