Hey Dan, would the one pictured in your post have been the only tach used until the Rotunda was worked into the mix in the 21xx range?
That was the mechanically cable driven off the rear of the Lucas® generator tachometer model that A.C. Cars installed. The electrically operated Ford-Rotunda tachometer with dash hole size reduction adapter was introduced when HP289 engines, Ford voltage regulators, and Ford HP289 generators with machined from bar stock sheaves were introduced and that happened as the new specification in the CSX207x range production wise.
Lucas® brand generator with an A.C. Cars designed and provided one piece cast aluminum large diameter fan and sheave

Lucas generator, A.C. Cars sheave, Lucas gear drive adapter, and cable leading to under dash.
