Want to put and aftermarket tach in a rallye dash

This is kinda the plan, Whatever i get, i am going to remove it from its housing, and ditch the glass, put it behind the stock gage glass with the raised center nub to make it appear stock. Only want to hook up the power, gnd, tach feed. Let the cluster lighting backlight it. Yours looks good bodyperson, but dust and dirt can get inside the cluster if its left open back there.