Here's one option
http://www.jennycraig.com.au/home/
Is it an IRS or a Live axle? It sShouldn't be to expensive to narrow the rear end housing if it's a live axle. You could probably even get your axles resplined rather than new ones.
I just went through the whole excercise of narrowing my IRS rear end by 2" each side. Not an easy job.
Cheers