can you put a external tach on a stock ignition? if so please tell me how thank you

 

You can put a tach on any car. How to do it depends on the car (as for the wires) but you basically find the tach lead (if you have a stock tach) and tap into it for your new one. The instructions should come with any tach to tell you how to install it. It's been a while since I did one so I can't remember wire locations/colors/etc.