Here's some significant assembly done, finally, on this thing. I managed to get the engine bolted to the frame. This was not easy... Getting the steering gearbox in place was especially tricky. All these components, the frame, engine, floorboards, etc, have to go together sort of all at the same time in order to work at all.
The good news is that my idea of moving the radiator fill back by altering the part a little worked well. It gives enough room that the engine only had to be moved about 1mm and it all - sort of - fits! The hood will work fine, no gaps.