First thing I thought of was steering dampner, but you said that's been changed already. Regular shocks too?
Could also be really wonky front wheel alignment, the joints for the steering knuckle, I'd also inspect the rag joint and steering box.
Not much left to check though, really.
Oh, here's another I just thought of. Is your transfer case locked in position maybe? how is the condition of the front differential?
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.