This is a back side of Nakajima HOMARE Model 21 engine for any references.
The wooden stand size is different from that of Mitsubishi Kinsei 45 as Kinsei is much bigger than Homare.
According to my research, the appox. size of the wooden stand for -
Nakajima Homare : L1600xW1150xH800mm
Mitsubishi Kinsei : L1900xW1300xH900mm
Thanks.