Sounds like he will be running two antennas. One for CB and the other for the scanner.
Install is still the same. Place the CB antenna near the center of the cab (provides best ground plane) and you can still route coaxial cable down the "B" pillar. As for the scanner antenna, place it on the rear of the cab above the center high mount stop light. You can either route the coax up to the "B" pillar or route it down the back corner of the cab.
Unless a diesel or a truck with the dual battery option, I always hated the idea of running power over to the driver's side.
These were all 5.3l gas engined trucks. Using proper installation techniques and the right size power cable it isn't an issue. GM has been putting the batteries on the passenger side of the trucks for a few years now and I haven't had any issues with them. These have all been 50 watt VHF mobiles.
Even less of an issue for a CB and a scanner where you'll be looking at 5 amps or so at the most. It's pretty easy to route the cable up high along the fire wall and stay well clear of anything hot or sharp. In fact, if I recall correctly, there isn't any other wiring up there anyway, so less of a chance for introducing interference.
I do believe these all had a spare stud on the + battery cable that we tied into. I think there was either an installed ground lug nearby or we were able to add our own pretty easily.