With the prices of Smiths Classic Gauges going through the roof, I gambled at eBay and won this for about $20/shipped. It is an RVI* 1433/01 negative ground probably pulled out of a junked mid-60s MGB, MG Midget or Austin Healey Sprite.
*The RVI Series only works with conventional contact point ignition systems. For later models (or converted) with electronic ignition, use an RVC.
NOTE: the black dotted lines between the distributor and coil denotes a wire that should be removed. Essentially the tachometer replaces the wire and, is in series between the distributor and coil as shown in the diagram.