The steels are the steel ring that is part of the wiper kit and the steel backing plates that hold the wiper assemblies to the knuckle. They don't come with the rebuild kit and I like to replace them, if for no other reason than I hate doing that much work and having rusty nasty backing plate that I have to look at. Neither are usually needed because they don't really wear out. The brackets get dimpled, but you can straighten them easily enough with a ball peen hammer. Cruiser outfitters has a knuckle wiper kit for $15 a side that comes with the steel parts. If you get that and the rebuild kit you'll have extra felts and rubber wipers.
The rebuild kits available through Cruiser Outfitters, marlin off road, or CruiserDan usually don't come with the steels. You can decide if you want to replace them or not. They are available from all those places. Make sure they come with wheel seals and an axle seal, even if you don't do wheel bearings. They all provide kits with or without wheel bearings. I usually do them because then I know the wheel bearings are good, and if the old ones are serviceable I have spares.
http://www.cruiseroutfitters.com/seals.html
Lots of people are fine with the early small pattern knuckles and coarse outer spline birfs on the street. I don't see the point of doing all that work and not putting the bigger parts in from the later trucks. They are plentiful enough that they are not usually very expensive. You will need the knuckles, birfield joint and fine spline hubs. You will also need steering arms for the bigger pattern, but with the smaller TRE taper. 60 series knuckles will work, but 60 series arms will not.
The Aisan hubs are getting more expensive, but you will not break them. The warns can break, but again, lots of people do fine with them. My 45SWB has weak hubs (Selectros) but they look great and work fine, especially with an open front differential.
Longfield super axles means you never, ever have to worry about breaking a birfield joint.
Now that I have Aisans, Longs and six-shooter (six upper studs) knuckles I really don't worry about my front end any more and I wheel reasonably hard.