As others have mentioned, you could add the crank pulley of an A/C system onto your 8.3. I have the A/C kit and it includes a bolt on crank pulley. If you want I could send you the dimension and you could have a machine shop fab you up just the crank pulley add-on. You have to space out the fan drive also in this case, I think the blades hit otherwise (?). Another crank option would be to ask truck boneyards if any 8.3's have a different or multi groove crank pulley you could buy and add.
Three other options would be:
1. Double belt alternator pulley, you could simply make one yourself by hollowing out a spare one (lathe) and having it TIG welded onto your existing alternator pulley. This leaves the crank pulley alone, and you have a lot of room above the 8.3 alternator to add a belt driven hydraulic pump (Northern Tool, etc...). Then you could do V or serpentine type.
2. Use the power steering pump. I added a MileMarker hydraulic winch from a Hummer H1 onto my flatbed towtruck front bumper, and it uses the truck power steering pump, the configuration is easy as the winch goes in series between the pump and the steering gearbox. I believe the H1 is like this also, and it uses 24V solenoids. It works fabulous and fast, even at idle. Never had a problem with it or the steering. Study their simple system, use their solenoid valves, or scale it up accordingly if need be. You can easily order 24V hydraulic solenoid valves and mounting blocks. I'm doing this to convert the winches on my M925A2 to be switch and remote operated, and ditch the cable operated tower (making it single person usable and safer in my opinion).
3. Replace the 24V hydraulic pump motor with a 12V hydraulic pump motor, but feed it 24V. I have read several articles where guys have done this for years on end without trouble. With a plow duty cycle being so low, I wouldn't hesitate to try this. The articles I read were I think on here, and guys doing it with dump bed hydraulics, which run much longer than a plow pump. This should double your flow if all else can handle it.