All the rally cars I've built for many years have exactly that bracket. I buy a length of 2" wide x 1/4" thick aluminium strip and some 16 sw (1.5 mm) thick sheet steel, then make up the bracket to the design you can see. I make up top steady straps from a pair of long Jubilee clips which go back to the front panel.
For rallying, my idea is that if I 'go off' and hit the front, the brackets supporting the lamp bar will bend before the front panel - it works, as I've proved!
With the depth of those Cibie Super Oscars I had to add a small extension piece to move the lamp base forward a bit, but for normal spots, including the famous Lucas SLR700, they fit without modification.
To bolt the mounting brackets to the front panel I use M5 RivNuts with socket head cap screws.
If you want, I've a photo of another rally 'S' with that lamp bar and 4 7" Lucas spot/driving lights on.
By the way, the centre strap is exended to meet the lower part of the front panel thus adding a bit of extra support.
Edited by Cooperman, 19 January 2012 - 09:24 PM.