user: Question: What chassis was used with the Chevrolet engine in 1991?
Columns: ['Year', 'Chassis', 'Engine', 'Start', 'Finish', 'Team']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1985.0, 'Lola', 'Cosworth', '20th', '7th', 'Bettenhausen']
SQL:

assistant: SELECT "Chassis" FROM "Table" WHERE "Engine" = 'Chevrolet' AND "Year" = 1991.0;