The only information about this mower is on ODK ,there is only one complete mower that has been seen online that I know of ,if you scroll down on the following page there is the one that was recorded here.
You can see on your mower base it has the same engine mounting holes and slots and the self drive U shaped casting at the back for the self drive unit.
The original early sixties motor looks like it could be a LV30 from Barclay Trading Company as they imported motors from USA and sold to other manufacturers in the early sixties.