How are you powering the SDS? I'm going to assume strictly battery for now, so:
1. willing to bet the LED bar is a cheap chinese brand from amazon, which isnt even SAE compliant, so first suggestion is throw it in the trash.
2. Ferrite choke on the power wire for the lightbar.
3. Dedicated power run for the lightbar. Power direct to battery, ground to body somewhere reasonable.
4. Do NOT under any circumstance run a cig plug cable for the scanner and a cig plug in the same outlet to the lightbar. In fact, a dedicated power run to the battery for the scanner is also a great idea, with a ferrite on it as well.
5. A bonded antenna is your best bet. If the mag mount is a NMO type and the whip comes off, switching to a NMO mount will probably help a lot. Consider a fender mount to get it away from the lightbar, unless you have some type of rack system in the back that you can mount the antenna to. Since its a work truck, drilling the roof type NMO probably isnt an option, plus you want to be further from the lightbar anyway.