Go RNR.... way less than the PSC option. You may find yourself in need of an upgraded pump, you may not. Depends on how you feel about the low RPM issues (some claim to have none, some claim it is enough of an issue to upgrade the pump). So with the RNR, you are looking at 500 (or 900 w/PSC pump).
PSC will cost you around 1600.
One thing to note with the RNR, you have to send them your box... so you'll be down for about three weeks.
Then... of course you have to relearn the way you drive. Hydro assist maybe wonderful in the rocks, but on the street not so much... sneeze while going down the interstate at 70 and you'll see what I mean.
BTW.... can't think of anything anything else this side of full hydro that will address your issue.
EDIT: Plenty of people have 37s and bigger without steering box issues. It's no fun to end up there, but don't be frightened into needing this. It is purely a functional upgrade, nothing to do with safety. If you are excessively worried about steering box strength, they have products on the market to address this that are MUCH less expensive.
Last edited by abendx; 09-06-2010 at 01:12 PM.