[SymeAaro (OP)]

Before you answer:
Many different sources say different things. For example:
Different NASA journalist sources say either that each has 375000 lbs, or 418000lbs
Wikipedia says 418000 lbs, based on the Aerojet website, which says the same.
However, Dr. David Baker, a editor of spaceflight, who worked as an engineer on NASA apollo, Gemini and space shuttle programmes, says they each have 550000lbs of thrust. He also backs this up with a story of the history and development of how the SSME came to be like this (as part of a race between Aerojet and Pratt and Whitney).
Into black, a novel of a true story of he space shuttle, says the same, with the same story to back it up, and the author has researched many sources and interviewed NASA members.
Who should I believe?

[Kryptid]

There is no one thrust value produced by a rocket engine. The thrust produced by the Shuttle depends upon the external conditions (atmosphere vs. vacuum) and the throttle setting. This might be of help:https://en.wikipedia.org/wiki/Space_Shuttle_main_engine#Engine_throttle.2Foutput