More than twenty years ago, in the February 1978 Word Ways, I challenged readers to find a set of eight seven-letter words in which every one of the 28 possible pairs had exactly one crash (one letter-match in the same position, as foRce and maRy, or caSinos and miSrule).
Eckler, A. Ross
"Every Word-Pair In This Set Has One Crash,"
Word Ways: Vol. 32
, Article 2.
Available at: http://digitalcommons.butler.edu/wordways/vol32/iss1/2