Many thanks, that image answers a lot of questions of how the mounting tabs project.

Can the box be installed from above or does it need to go in from another angle - is there enough clearance ?

it is installed from above. just drops in place.

I'm just going through completing all the wiring and connections, including the voltage regulator I located on the back of the rectifier mount under the tank.

All colours matched up ok, and lot of connectors required a good clean or replacing. Then I was left with just one lone orphan wire - pale blue for the neutral switch, which my engine doesn't seem to have - or if there is one its not in the normal Yamaha location on the end of the selector drum. And there are no wires from the main loom that would indicate that there is one.

So am I looking in the wrong location ? both manuals I have do show a neutral light in the wiring diagram.

No neutral light on the 73 250/360.

+1

Where is this lone wire Jools and do you know its source? If it is coming from a warning light in the tacho, then you have the wrong tacho . This is not unusual and I had the same issue with my RT2.

Thanks for confirming that guys. Yes it does come from the tacho I think. When I was assembling missing parts back in New Zealand 20 odd years ago living in a dairy farming community, I used to rummage through the local breakers shelves looking for bits and pieces, so its not surprising - plus the red line being too high gives it away !
I can live with that for now as it will be a rolling resto and no way a show pony.

Was the DT3 generally an American market bike ? I guess some must have made it to NZ.

Plenty of DT3's came to New Zealand . Not so plentiful now however .

And a handful, in slightly different spec, might have made it to mainland Europe, but not the UK. However, quite a few are now being imported from the US to the UK.