From what I understand, the first episode of Super Password to feature Gene Wood whispering the passwords was the Monday episode of the Abby Dalton & Richard Kline week. During the entire first puzzle, Bert mentioned it on the air, after he had been talking through it.
Also, GSN skipped over that week in 2006 and last year, yet they had no problem showing that week back in the 90's, not to mention the fact that there are no celebrity clearance issues with that week. Sometimes, GSN does things that are definitely not self-explanatory and are too hard to figure out, this being one of them.
That week would have been episodes #0540-#0544, assuming that Bert also mentioned the passwords being whispered on the first Newharts & Martins week, which also aired in 1986. The Newharts & Martins actually never had any issues about their Super Password episodes being on GSN, even before 2007. Chuck Donegan even stated that he remembered seeing them on an episode that aired on GSN before 2007, but I don't know if it was from the 1986 week, or from the 1988 week. And was it during the normal rotation, or for a special occasion? If so, what kind was it?
Keep in mind that when GSN used to have the rights to the G-T library, their digibeta copies of the episodes typically had 3 per tape.