Reliable information for an Opel Omega can be found at the official Opel website. They have a comprehensive database regarding all their released models.
The Opel 1900 wagon was produced from the years 1966 to 1971. The maximum speed of a 1973 Opel 1900 wagon 4 cylinder 75 HP is around 110 miles per hour.
The Opel Astra 2.0 16v engine is an interference and non interference. This is one of them most important aspects that any potential buyer should check. Interference engines rely using timing gears while a non interference engine has a piston that does not go anywhere with open valves.