Complex sentence: The design was revised in 1963, with the new version designated Lark 1B, and plans for this version were offered for sale from 1968 and were still on sale into the 1980s.
Split into simpler sentences: The design was revised in 1963, with the new version designated Lark 1B. Plans for this version were offered for sale from 1968 and were still on sale into the 1980s.