1985 Jaguar XJ6 My car overheated and locked up the engine

1985 jaguar XJ6 6 cylinder mileage: 100,000. My car overheated and locked up the engine, I had been contemplating replacing the original engine with and American brand (Chevy 350) however, I now would like to rebuild the engine. What I need are the engine specifications and torque. If you can be of any assistance, it will be highly appreciated. Also, if you have any other suggestions please feel free to advise.