If you don't have a dash panel in your vehicle, this mounting cup may be the answer. The base can be screwed down to a panel or tube, or hose-clamped to a tube. The cup pivots nearly 90 degrees vertically to adjust the angle between the cup and the tube. It does not swivel horizontally, so the tube will be parallel to the cup (in other words, you cannot clamp this mount to a dash cross-bar -- the gauge would point to the side of the car and not to the driver). Accepts most 2" diameter gauges*.
* Note: Fits all 2" Auto Meter gauges. Some other gauge brands may require some modification to the mounting cup.