Kenworth T800 Audio

Hey guys. My brother in law would like me to install speakers and a head unit in his T800. Not being familiar with the truck, i don't know how many speakers/what size they are? Factory amp? I haven't seen the truck yet as it's about an hour away from me. I'd like to get the stuff ordered (head unit, speakers, harness, dash kit) and head out there with it all in hand. Any help would be greatly appreciated! Also, i assume the CB uses it's own set of speakers?