Chances are the booster in the kit you use will not have a filter. Probably will have a plastic check valve. Don't worry about any of that. Never heard of anyone worrying about that. The booster draws in air around the foot pedal rod. No filter there. The vacuum is from engine vacuum. Some say the filter would be to protect he engine. Check valve stops backward flow towards booster. Some people say it keeps "fumes" from entering the booster. There was a recall re diaphragm failure allegedly from fumes. Just a bad choice of diaphragm material at the time. No filter necessary. The charcoal filters are from an emissions panic attack.
The disadvantage of under the floor is it can be difficult to check level and to fill. Some use a mirror or finger, some cut a hole in the floor, some use a remote reservoir on the firewall. Once properly bench bled and then system bled, you should not have to worry about checking level very much. The kits used to come with a squeeze bottle with a hook shaped tip so as to add fluid.
On your truck, you may have to reroute the Ebrake cable. All instructions come with the kit and thousands have been installed.
