JoeyCap, I would use a step bit as rwilimo said, if you don't have one you can start out with a 1/8 bit and work your way up (trying the antenna each time before you drill again).
I would imagine that yellow end stays on, the hole looks to be big enough for all that to go in. As long as the hole is not bigger than that foam seal it should not leak. I would drill the big hole first, then dab a bit of nail polish or something on the end of that little peg, then line the antenna up over the big hole and lower it down until the little peg touches, now your second hole should be marked right where it needs to be.
After you get the holes drilled make sure you clean them of any burs, and I would even go as far as laying some plastic down or newspaper to cover the cab and then mask off around the holes leaving about an 1/8 inch around the holes and spray a dab of paint to seal up that fresh bare metal.
I'm assuming that smaller hole is facing the rear of the truck?


F250 SD CC, looks like Ford left you some goodies under your antenna.



I wonder if an antenna like that would work for AM/FM, I would love to get rid of that OEM whipper off the passenger side.



SD Dually

 

Hope this helps.


SD Dually

 

Luckily its not mine......thats just a pic from a google search to give him an idea of what holes he had to drill into his roof.

Don't have an xm antenna on mine, dont want one!!

 

I installed a Kenwood radio with Sirius xm and GPS, all came with magnet antenna. To chicken to drill holes in my roof.

 

So I ended up installing the antenna this afternoon. I wish I would've seen SD Dually's explanation and picture, it would've made me a lot less nervous doing it! The hole size was exactly what he pointed out in the picture which turned out to be 5/8". I drilled it with a step bit.

The only difference in SD Dually's picture is that the hole can't just be smaller than the size of the rubber gasket. It has to be exactly the size of the white plastic piece because that clips in to the metal to prevent the antenna from pulling out. That metal collar/washer expands as you tighten the bolt, which tightens the whole antenna and compresses the weather seal.

I didn't think about painting the tip of that point, but I drilled a couple of practice holes and that point is exactly 3/4" away from the larger hole. I applied RTV silicone around both holes before tightening the bolt just for extra weather sealing.

I think I psyched myself out about this one, mostly because I couldn't picture how the antenna would tighten to the roof. Once I drilled a couple of practice holes it totally made sense.

I wouldn't hesitate to do this again over mounting a magnetic antenna. I hope this helps anyone attempting to add one of these in the future!