3 ways to run rear steer using engine-driven pumps:
A: 1 pump, everything plumbed together like John posted diagrams for. This is simple but as already stated, only one end will ever have full power at a time. You can easily learn to drive around this but its sometimes annoying. Back in the day this is how mine was.
B: 2 pumps plumbed together. If you do this you need to run check valves in the pressure line right after each pump so that if one pump dies it isn't fighting your other pump and / or pumping backwards through the dead pump. The main reason to do this would be to obtain more displacement / speed if you wanted the rear to move faster or were running a huge orbital that one pump couldn't keep up with. But like above, only one end ever has full power at once.
C: 2 pumps, completely separate systems. This is the super-pimp way to do it and what I have now and will never go back from. This is simply awesome, IMO. No compromises. You have full power at both ends all the time in unison, can do whatever you wan whenever you want without waiting. I have foot controls for my rear in my rig and use them 100% of the time. I NEVER use hand controls any more. My brain has become almost fully adept at controlling both front and rear simultaneously and I love it. Ask any of my friends, I can zoom around the woods, tight turns, around trees, on the trails at speed controlling both ends just fine. I can absolutely leave people in the dust in tight hairy stuff even with rockwells and 120" wheelbase because I can easily control both ends at once as if I never did it any other way. I have poor rearward visibility and have been in the front of a line before just chugging along through the woods and then eventually realize no one is behind me. I then sit there for 30 minutes waiting for them to catch up. Its hilarious.
I'm a rear steer junkie. I love it. I would have rear steer in my daily driver if I could. Every day I park in parking lots I wish I had it and after rides for the next couple hours I find my left foot stomping the spot in my DD where the controls are in my buggy without even thinking.
And yes, I do sell dual pump brackets for LS engines: http://patparts.com/product_info.php?products_id=36&osCsid=3ce5a6c50194d585b8e5b509697ebcdf
In that thread about rear steer valves I prefer my current setup to the one that b.boyd posted only because it has a pilot-operated directional check valve in it whereas the standard spool valve like b.boyd has does not. My spool valve always had a very slow leak to one side that got a lot worse as it aged. There was no valve to prevent it. The pilot check valve prevents any leaking and keeps the tires where you leave them. This is a very minor quirk though.
