Tony,
I have always towed my vans using standard Falcon wagons with H/D towbars. Have always used torsion bars and chains and never had a problem with sway or wallow.
One tip, if replacing the draw bar, make sure it is extended back to as close to the middle of the van as possible. Mine have been stitched to the front spring shackle mount. This minimises the load being transfered through the van chassis which can be a little flimsy in some vans.
It is not real cheap to do properly but well worth it.
I would
guess that an engineering company would hit you up for somewhere between $800 - $1200 including material.
No idea what mine cost as I was owed a few favours that I called in
Cheers Mark