I have the RTE arms on my Disco and they worked to correct my castor. The SG 3 link is also adjustable for castor correction ( I believe however, I've never used one ), OME makes castor correcting bushings as well ( I've never used those either ), and the True Trac I hear makes the castor issue less noticable however, it's not really a fix it's more of a cover up in my opinion.
Fixing your castor will rotate your pinion down which isn't a bad thing if you are using the stock drive shaft since it will put your pinion closer to the factory angle that it was at before the lift.. It will kind of correct both steering and driveline angles at the same time... However, with every truck, your results may differ from mine, so what works for me might not work for you.
If you were going to use a DC driveshaft then you would want to leave your pinion angle alone for the most part ( depending on the angle it's at now ) since the DC shaft wants the pinion angle to be pointing at the transfer case.
The reason that I bring up driveline angles is that when you change the rotation of your axle to correct the castor via new arms, bushings, and the like, then it also changes the pinion angles which in turn affects your driveshaft angles..
See this link to Tom Woods website for lots of good driveline info.. http://www.4xshaft.com/driveline101.html
edit: short answer - ya, corrected arms should get your castor closer to where it should be.