Thanks for the link. My trailer is 1500 x 1200 and I've built it from scratch (or rather had others build bits and I've put it together). If I can assist with what worked for me let me know. I got an AT35 hitch and my 245/75/16 spare just gets over it when I open the tailgate. An expensive hitch but a good one. The hubs are the VC ford 150dia and they work well with the KJ steelies. VC were good with helping to work out the total axle length. Check out
www.vehiclecomponents.com.au
Be wary of the spring over axle conversion. You should measure how high off the ground that will make the hitch considering the KJ wheels and see if this matches your car. You may also think about changing the springs to shackles and not slippers. Just more money! If the centres of the hangers suit it could be a relatively simple conversion.
Keen to see what it comes up like!