Induction tachs are installed in/out engine, just wrapp several rounds of provided wire around plug wire, will need to program the firing sequence though for engine to read well rpm achieved. Just follow tach's installation procedures and you'll be fine.
Better yet, buy a hour/tach meter. Will record elapsed runing hours, perfect for preventive maintenences: leg oil, spark plug, valve adjustments, oil & filter changes. Hardline has a much friendlier installation, just one cable which can be cut to size after tach/engine final cable routing, while TT doesn't.