Passage: This period featured teams managed by road car manufacturers Alfa Romeo, Ferrari, Mercedes-Benz, and Maserati; all of whom had competed before the war. The first seasons were run using pre-war cars like Alfa's 158. They were front-engined, with narrow tyres and 1.5-litre supercharged or 4.5-litre naturally aspirated engines. The 1952 and 1953 World Championships were run to Formula Two regulations, for smaller, less powerful cars, due to concerns over the paucity of Formula One cars available. When a new Formula One, for engines limited to 2.5 litres, was reinstated to the world championship for 1954, Mercedes-Benz introduced the advanced W196, which featured innovations such as desmodromic valves and fuel injection as well as enclosed streamlined bodywork. Mercedes drivers won the championship for two years, before the team withdrew from all motorsport in the wake of the 1955 Le Mans disaster.

Question: Where was the engine placed by engineers in Alfa's 158?
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