Did they change the style of the t-tops at anytime during the third gen?

Yes, they did. The early years had tops with hooks to hold instead of pins. There were also C&C tops, which were different alltogether, as they were aftermarket tops added by a different company (the C&C tops may be the ones with the hooks, I'm unsure here - these were 1982 - 1983 or 1984 cars). The later years had factory glass tops, until 1990 maybe? when the switched to Lexan plastic tops. The Lexan tops had larger pins than the glass tops, but they were the same shape, and thus swappable with one another. Most Lexan top owners look for glass tops to swap, because the Lexan cracks up from sun heat and looks bad from the inside. My car is a 1992, had Lexan tops, I swapped for glass. Firebird and Camaro tops are swappable between the two. That's my limited knowledge.

My t tops fit on both cars; 86 - 92 except the 92 has lexan's