Just did this on my 2015. I used a fuse tap on the driving light fuse in the cab fuse panel. Check your manual to see which fuse it was because I forgot. Works perfect with the light switch/auto lights. Also works whenever you lock/unlock the truck. Works perfect for my new interior lights!
I ran a tap off the interior light switch for mine. I'd consider splicing off the fender lights. Might be a long lead to run but it's an easy pair of wires to find on each side.
Really don't want to run wires into the cab. I guess I'll tap into the fender lights. I was just wondering if there was a tap somewhere like the dead ended plug for KR running board lights.
Interior is easy to access either thru the firewall grommet or the body mount opening under the carpet. The firewall grommet is best accessed if you pull out the driver's side wheel well liner. There is a short "extension" that you can cut on the very end to pass the wire to the inside.
I'd determine the total wattage before just tapping in to an existing circuit. Even LEDs can overload a circuit. Best option is to tap on a trigger to a relay and then have a fused dedicated circuit.