Hi Dennis and welcome to the forum! I've moved your post to here where it will get more views.
By super steer valves are you speaking of the Motion Control Units? SuperSteer Motion Control Units
If so a call to Henderson's, or wherever you bought them should clear up the questions. I had them installed on my 40DP three years ago and think it was a good investment. Not a miricle cure all but made a noticable improvement.
I'm not sure you can assume anything about the GVWR of a 39' DP but 30K would certainly be on the low end IMHO.
Best of luck...