Very strange for such a valuable car to have the engine coming from a fire engine's water pump.
Considering the Climax's excellent specification, necessary for it's designed application, its being repurposed as an F1 or featherweight sportscar engine was a stroke of genius in thinking 'outside the box'.
When I was an apprentice at the Navy Dockyard in the late 80s/early 90s, I was surprised to find a plethora of portable Coventry Climax powered fire pumps laying around. The pump units were regularly abused by their operators in ways only a sailor can, and so the engine shop was overhauling them on a regular basis. In those days my head was more focused on American muscle cars than sports cars, but I liked sports cars too, and the significance of these engines was not lost on me. Eventually they were superseded by more modern units, and one day I went snooping around the shop to see what obsolete bits might be hanging around. I learned that all of the pump units (possibly 20 or more) went to a Crown Assets auction (where they would have been picked up for a song). But horror of horrors, I also learned that just a month earlier, during a shop clean-up, dozens of OEM overhaul kits and hundreds of spare parts of all description (pistons, cranks, everything) went straight to the dumpster.
In amongst that lot would have been a significant number of parts that I imagine would be exceedingly difficult or impossible to find at the time, not to mention, today.