Here's a set of rear axles for $50 plus shipping.
http://www.pirate4x4.com/forum/showthread.php?t=536720If that's too narrow you could run a FJ80 land cruiser rear. It has the same basic 3rd but is wider to begin with, so if you narrowed the long side to match the short it would still be wider than the FJ40 rear. The FJ80 is also a full floater rear, so if you did have to get axles made it would probably be easier and cheaper.
