Are you sure that its a mechanical one? Most of the AM oil pressure gauges are electric,and come with a sending unit,and harness.Then you just have to run a T fitting for the stocker and autometer one. Running mechanical gauges inside the car is a mess waiting to happen...if it is a true mechanical gauge,it will have a brass fitting on the back of the guage,and they tend to always leak.....just like the fuel pressure one. Also,most tracks wont allow you to run if you have these types installed in the interior due to fire potential.