Much like me, it ain't pretty, but it does work. I took a piece of 1.5 inch round stock and milled .125 off a section of it. This gave me a flat area to screw the lower to, and, it also centers the buffer hole (which is .625 above flat) when bolted together. Still have to center it side to side, but, that is pretty simple.
I drilled the holes to match those in the fixture. I bolted everything together, then, removing one bolt at a time, I used an end mill to make a flat so the bolt would tighten down straight, instead of angled, so it is nice and solid. Repeated for all three holes.