the one we are looking at is rated for a maximum axle load of 3200 pounds. so We are thinking it should be ok for a 404.
Its not cheap, but its simple, should be reliable, wont rob the mog of precious horse power and has many other benefits..such as being able to adjust the amount of assist on the fly.
Unfortunately in Australia even fitting a simple tourque generator steering setup can cost around 1400.00..which admittadly is half the cost of a electric setup but without the benefits..and we have done this and the results are great off-road but useless onroad.
Will probably fit it up to a 710K Pizgauer first and see how it all goes.