I was not aware the Ha-54 was built
Here above you even have photos of the preserved Ha-54 engine that was found in Japan.
Hmm, Ha-50 was a different engine from the Ha-54. Ha-50 was a 22 cylinder, and the Ha-54 was 36. Though I admit I don’t know if the Ha-50 was for the G10N or not
I honestly don’t know where the Ha-50 engine suddenly came from. Sources I’m familiar with say the Ha-54 engine was intended for the G10N.
By the way, I found this:





