I've entered all the solutions as I see them but still puzzled by the rubric - "Solutions to four across and four down clues require a letter to be changed before entry in the grid. All these eight entries are of a kind.". Can't figure out any connections at all. What am I missing??
If you look carefully you will find 8 answers (4ac, 4d) where if you change 1 letter in each you will end up with 8 new words that all have something in common. All letters to be changed are non-crossers - 5d is one of them.