So a tach from autometer isn't going to be as accurate or as good as one of these?

 

i have the stock censor for a tach is there a way to hook that to a lets say a autometer tach

 

If the tach is not specifically for diesels the it probably needs a 12v signal.
The diesel tachs need a 5v signal.

You could wire up a 555 IC and a couple of resistors and capacitors to provide a 12v signal for every 5v pulse from the CPS. Not a lot of work but it is work.
Just find a tach for a diesel - easier on the nerves.