There is an aftermarket kit for mounting an air compressor ontop the alternator, you put a differnt pully on the alt, an it runs a belt for the compressor. the industrial b-series run the cummins air compressor off the gear housing. where you would have your vaccum pump and ps pump on the dodge, you have the compressor and hydraulic pump.
Ah air brakes. Well SRath, i must disagree with you here. there are many more advantages to air brakes over hydraulic brakes, and dropping and hookings trailers is by far NOT the only reasons class 8 tractors have air brakes. if that were the case, why do strait trucks, rollbacks, coach buses, etc, use air brakes. it all boils down to one main factor, SAFETY. air brakes are much more reliable than hydraulic brakes in the event of a failure. for example the park brake system, for those not familiar with a spring brake chamber, the chamber has two seprate halves, one half contains the coil spring, that has enough force to litterally take off a mans head, the other half is just an empty chamber with a diaphram. when you mash the valve in the dash and release the brakes, air is applied to the spring side, the psi on the diapram overcomes the spring pressure and compresses it, therefor removing load from the slack adjuster and allowing the S-Cam to rotate back and the shoes to pull away from the drums. when the service brake (foot pedal) is applied, air is sent to the other half of the chamber using air against the diaphram to push the rod connected to the slack adjuster and apply the brakes. for the record, air brakes are MUCH more sensitive than hydraulic brakes. with hydraulic brakes, when you push the pedal you are using the force from your leg to push that fluid to the calipers with the help of a booster. with air brakes, when you push that pedal, you are simply opening a 2 stage valve and allowing a pressure that is already present to flow into the brake chambers. that is why they are so responsive, because youre opeing a valve with near 120 psi behind it. thats why when tractors bobtail they can lock up the brakes so easy, because they are so touchy.
in the event of a leak in the system, with hydraulics, your SOL, once your precious fluid is gone, you can kiss your braking ability by by. with air brakes, the compressor will continue to pump air as long as it needs untill the governor opens the popets an lets it free wheel. if you are hauling a load, and blow a brake like, say its hydraulic, there go your brakes, no chance of stoping, if its air, then the spring brake decompresses and the brakes are mechanically applied. that is the beauty of air brakes, with out air the vehicle can not move. there are some awesome valves out there for differnt applications too, for example, say you got a 53' with 80k on it, you loose tractor brakes, you cant stop that load with your foot pedal now, but you can pull the trailer hand valve and apply trailer brakes to come to a stop. you dont have this option in a strait truck, so if you loose primary air (air used to apply drive axle brakes and release park brakes(the park brake stays released due to air being traped by a check valve. )secondary air is for steer axle brakes and accesrories) youve lost all but your steer brakes, but when you apply the brake pedal, it uses the secondary air that you have, to activate a valve that releases air from park side of the chamber to produce a mechanical application at the drive axles. this can be repeated 8+ times before all air is exhausted and the brakes lock down.
as far as lines icing up, a good driver should drain his tanks daily, at the least his supply tank. if he fogets and gets some condesation build up, shame on him, dump a little alchohol and get back on the road. another practical benifit of air brakes, ABS, with hydraulic, you have to recover the fluid in an ABS event, with air brakes, the air is simply exhausted. hydraulic brakes have a bunch of componants to deal with to, fluid resevior, booster, master cylinders, slave cylinders, calipers, wheel cylinders, etc. air brakes dont have too much more than that, compressor, governor, airdryer(not neccesary), tanks (thats the bulkiest part of the system), chambers, slacks. and with the access of air, you can run air ride suspension, air horns, air ride cab, air ride seat, air lockers for drive axles, air locking hubs for 4x4, the list goes on. dont mean to rag on you, or chew your ear off, but i love air brakes, and am pretty pasionate about them. if it was my way, there wouldnt be anything but air brakes, i know a number of ole boys that would agree with that statement