I suggest this PV4 valve: CLICK HERE
Call their number to make sure this valve is also used for drum/drum applications.
I like it because the mounting holes are part of the casting. 1/4"-20 bolts fit. Most of us mount the valve on the fender apron, then plumb to it. The M/C brackets use space under the M/C, making it harder to change spark plugs. If you mount to the fender apron, the valve is out of the way but still very accessible.
Here's an internal view...