On my roadking there was no manifold tube....my kit just bolted on, no mods needed. But you may be stressing over sumpin really simple....even if it involved drilling a few 1/2 inch deep holes and threading them..exactly where you need em. If you have the holes already they are most likely 1/4-20, or 1/4-24 threads(maybe 5/16). Get some of those metal wire holders that have rubber coating, to hold the tube in place.
Wish I had some close up pics...I could tell you more, sometimes you need to massage sh!t to get it to fit.
Step out of your 40 watt incandescent bulb world....and it will become purely simple to you.