NVU Universal fuel senders are designed to be the same size mounting holes(5-hole) and range (240Empty-33 Full) as the industry standard for aftermarket and marine.

Mounting holes:
If your tank came with pre-drilled holes, the float arm should already be in the correct position as the tank manufacturer has already figured out the best position for the float arm.  If this is not the case, make sure you plan ahead before drilling.  Ensure that the tank does not have any obstructions (pumps, baffles, etc) for the flat arm.

Setting the depth:
1. Measure the tank depth from the top of the tank to the bottom.
2. Set the fulcrum at the center point of the tank (half).  You can cut or mount the fulcrum on the upper arm if needed, as long as its in the center of the tank.
3. Slide the float arm in and out until the sender can swing all the way up and all the way down without hitting the top or bottom of the tank. (see pic below)
4. Lock down all bolts, cut off excess float arm (leave about 1" and bend 90 degrees on back side of nut to prevent falling out if nut comes loose).
5. Check for proper swing

Helpful hint:
Make a full size drawing of your tank on a piece of cardboard like the one below.  Lay your sender down on the cardboard like a template to check depth and float arm swing.  That makes things much easier.