Where you want them is up to you, really. Make a cardboard dummy, move it around untill you find a position you like. Use a punch to mark the holes, cover the mark with a little masking tape to prevent the burr bit from slipping, drill away....
Now there is another (rather more expensive) solution which might work: you can purchase a longer badge bar (for example from Heart of England) that almost reaches the overriders. Then the lamps can be fixed to the bagde bar close to the overriders, using a bracket. Stafford Vehicle Components makes such a bracket, intended for Lucas spots. It might work, but others make brackets too, check out HoE, Librands etc.
I have not tried this myself, and it might be that this setup puts too much strain on the badge fittings. Borghi i Milan makes a bar that actually attatches to the overriders, must be a lot more stable. Then you would have to order it from Italy.... Boils down to how much money and effort you are willing to spend and what you really are achieving.
