There is still the big wires held on by nuts, one from bat - to engine. One from bat + to sol and one from the sol to starter motor, the yellow is I presume an extra earth wire between solenoid mounting and the battery put on by a previous owner.
Yep that's the fitted position. It's the green wire in the middle that has no place to go on the new solenoid, could it be a live feed for long disappeared extras? Car was built in 75 but not registered till 1980 so could be an ex military??? Was told it had been in Africa