You can get a Aussie locker for $250. I've had mine for about a year now, installed it myself (first time I've ever opened up a third member), and has worked great since I put it in. It does take a little getting used to for cruising through parking lots, but other than that, don't even notice it, except out on the trail where it increases your offroading capability immensely.

84 Ext. Cab Pickup.