so I bought a set of cab lights and to save myself some money im planning on installing them myself. I drive a 96 f150, and for me this is very risky by drilling into my roof but im wondering if there is a write up or if anyone knows all of the correct factory measurements for the mounting of these lights it would be greatly appreciated thanks!

 

Place them on the roof how you want them to look. Measure and make sure they are all centred. Drill a hole. Run your wires down to the passenger side kick panel. Tap into the brown wire. Make sure you silicon around the holes

 

Put some painters tape (the blue stuff) down at the approximate location of the lights. This way, you can use a sharpie and mark everything without marking up the roof of your truck - even though the markings will most likely be drilled away. The tape also helps keep the paint from chipping while drilling, I think.
I measured 6" from the upper-most edge of the windshield rubber and put two rows of tape there. I then measured for the center and used a center punch to center the hole (of course, I measured several times to be sure!!). I then measured 8" each way from that center, and then another 12" from those centers. I took these measurements from a cab that had them at the junkyard (although I have no way of knowing if those were factory installed or not).
One thing about the above post - I did not use any silicone on mine to seal them. I have seen arguments for both sides, but I have never heard of factory lights leaking and they do not use any silicone - just the gray foam stuff that comes with the lights. Mine have never leaked.

 

The reason i recommend silicon is because it's not worth the risk of it leaking. Because it can cause rust in places you don't want it, and to protect that headliner

 

I ran a strip of tape along the front that followed the curve of the windshield then moved them around until I liked the look, then measured it all to make sure it was symmetrical. Make sure you double and triple check all your measurements. And use silicone as others have said, I put some on the rubber gasket and then on/in the screw holes, mine were eBay lights though.

 

How far from the outside of the window moulding did you measure for each to sit from the window?

 

I didn't measure from the side window molding. I measured for the center, then measured OUT from there. I found center, then measured out 8", then measured out 12". repeated on other side.