Online templates for mounting tuning machines?

I don't know of any off hand. What kind of head stock does the bass have? If the tuners are supposed to be mounted parallel to the edge of the the head stock, you can just use a straight edge. Install the tuners without the screws. Use the straight edge to line them up. Mark the screw locations. Drill and you are good to go. If they are at an angle, you will need an angle gauge or a protractor.

 

Or, just a good set of eyes.