Then how are y’all doing it? Drill a hole from above, run a fish tape to the edge, and pull it over and up that way? There’s a mess of side curtain airbags and other wiring in there, including my 3rd-eye brake light bed camera I installed for which I tried to avoid dropping the headliner to run it and failed. There’s also a crossmember in there somewhere I wouldn’t want to hit.
A true NMO hole saw will have a design that limits how deep it'll drill.
You drill the hole from the outside and then feed the cable in the direction you want it to go (to the side of the cab, or rear to the back) Then fish it with a coat hanger to pull it to where you can reach it.
Routing around the airbags isn't much of an issue. if you go to the rear of the cab, just drop down the back corner. If you go to the side, you route the cable up against the roof and above the airbag, then down the pillar.
Other option is to remove the dome light and visualize from there.
If you take it to an installer, they'll do the exact same thing, and hopefully route it correctly. Or, you do it yourself and know for certain it's done correctly. You can also make sure you are using good quality materials, not cheap Chinese antenna mounts.
You can do some research on where others have mounted their antennas, and hopefully they included measurements so you can go in the exact same location. Or, you carefully pull down the edge of the headliner and visualize things to avoid hitting cross members. Takes a bit of skill, but it's not difficult.
There's probably tens of thousands of heavy duty Fords of that era running around with permanent antenna installs.
I honestly don't remember the last time I actually dropped a headliner to do an install.
