Just a couple of notes about the coil procedure:
1: With bare wire coiled up that way, it's all shorted to the point nearest the insulation. Thus, the "length" of the bare wire is no longer than the point closest to the insulation where the coils all touch. IF the wire had remained insulated, it would have an increased "length". As it is, the only length gain you get is the insulated portion of the wire. Running it up the A-pillar that way, you DO receive an increase in the antenna's length. But the coil of bare wire is just a big, single wrap inductor.

2: The plastic or rubber insulation the wire used is covered with has virtually no impact on the radio waves used by the fobs. Leaving the insulation on, and making a coil that way, you make a large, heavy duty inductor. A single loop of the insulated wire does more to increase the receiver's sensitivity. The wire wraps on the CB antennas are insulated, and evenly spaced. This increases the antenna's length, essentially. One method that could be used is to wrap the insulated wire around the wire bundle, as evenly as possible. Using the wire's as a core, however, adds some capacitance that may affect the antenna's properties. It's response to the specific frequencies the fobs use.
The best thing to do, if possible, would be to run the added wire up the A pillar, and then across the front of the roof. Heck, if you're going that far, running the wire all the way around the edge of the roof gains the greatest length, and, being so close to all the windows, and windshield, allows for the best possible reception. There's a reason, however, that CB antennas, in the old days, were tuned by clipping short lengths of cable off until the transmit strength was maxxed out. Now, they're tuned at the factory.
I'd wager the receiver for the fobs in the truck is of the best length for the frequencies the fobs use. Adding wire just allows for better routing.

3: Just so you know my credentials, I was a Radar Technician my entire working life, with the Navy's equivalent of a BSEE. The final 15 years of my working life, I was the Lead Electronics Tech for a US Customs Aerostat site.

Have fun, all!
Pat☺