Drilling into the cab to install beacons?

Self tappers sure, with a dab of silicone.
I'd probably use nutcerts or rivets

 

I'm no expert, but if it was me, I'd use self tapping screw, but I'd add a flat washer and lock washer. So I'd put the soft washer first, flat washer on next, then lock washer. My thinking is that doing it this way will keep the screw from vibrating loose.

 

Trucks use a steel anchor, similar to a lead concrete anchor for mirrors etc. I’d try to get some of those from the Dealer. Concrete anchors might work, but usually are too big around. Sleepers are usually framed with 1.5”x1.5” or maybe 2”x2” steel framing. Looks like framing on plastic totes or milk or plant racks. Same type of framing as a lightweight fiberglass camper. Trucks metal panels are usually riveted to the frame. You can try to find a metal stud by looking for the rows of rivets. Better yet a bolt, if any. Drill into that area between a couple rivets, and put the anchor in. Use a bolt just long enough to work. Only way to be sure, is to take inside panel off and drill from inside side out. Might be best anyway. Maybe you can secure a bolt with a nut from inside of cab, leaving just a stud coming outside, depending on what the framing looks like. You can figure something out. That would make removing or changing things easier when needed.

 

Use rivnuts ( i believe its right name )
Used on mine ... Didn't install the light though yet

 

I’d also suggest riv nuts or nutserts .



Be careful drilling
Find a inner support as mentioned , and
You can stack washers on the drill bit so only the tip is exposed,
Otherwise , when it breaks through the metal , the entire drill bit will grab and pull through before you can stop it , and it will damage the interior panels or hit a wire inside .

been there , done that .

Also alot of strobe lights and LED lights will affect your radio, by making a crackling popping sound on the CB

very annoying if / when you use your cb to talk to the pilot cars .
So save the receipt and box and paperwork until
You know the lights won’t mess up your communications.