Is it possible to brace the steering arm?

[boostat4500]

I finally got my 71 Suburban back on the road after a long tear down for paint. I can't drive the thing in a straight line to save my life. It has 8" lift springs with 38x15.50r16 tires. The steering components are a drop pitman arm, drop ("S" shaped) drag link that's brand new, and raised steering arm with a Rancho dual stabilizer kit. The truck wanders horribly going down the road. I know the fat tires don't help. When I turn the steering shaft by hand, the only play I can find is the steering arm flexing. I can get almost a 1/8th turn just by hand with the engine off. There is no play in the steering box or drag link ball joints. Can the arm be braced somehow? I am most frustrated because I used to be able to drive this thing at 80mph and let go of the steering wheel no problem, it was that stable. The only change since then is going from 6" to 8" springs and the new drag link.