the XBR500 brackets match the original headlight of the 750Twins very well. I have just used some – estimated 3 to 5 mm – spacers /washers between holder and lamp to fix the headlight firmly without bending the aluminium XBR brackets to much.
Sometimes I am using a wind screen which holders fit in there without the spacers.
To fit these head light holders you have to move the fork legs out of the triple trees(?). They are a single piece unit, simple bolt on to a complete front fork is not possible.