I ran a Bates type light with stock harness doubled over a lot of the wiring bunch, and taped it. Tucked it under the stock tank.. Would pop out or hang down. I am sure you could hide most under there, and make a few longer wires to get where you need to go. Be much easier if you trim some of the unneeded off the harness .
I usually run bare clutch lever, a 70-72 right hand switch/throttle housing . That gives me Off, Low High for lights , kill switch, and starter button... I used that for the horn.
If its a 75 76 harness , you may not want to cut it , get another...earlier has less fuses ,no clutch interlock..etc