ssm shows 87 wiring diagram next is 95..
on the 87 only could find one yellow wire with white tracer..the common at the dimmer switch (high beam low beam  y/w to y = high y/w to w = low)..goes into 8 conductor connector ..
on 05 diagram 2 y/w one from the normaly closed set on the start sw to the 8 conductor connecter turns to b/r common for the horn and the pass sw(high beam flash)...

the 05 diagram must be the 2 y/w you have left over if horn works youre ok cause the 87 didnt have the flash to pass switch..
hope this helps...TC