[BLAZERMAN]

Here's one still available from any GM dealer, I've used this spacer and had no problems with them, if I remember another member said he used the same one and it broke on him.
Another option is to use the top plates from a 73 to 87 truck and go u bolts up, you won't need the spacer and its a much better setup. I've seen axle tubes half eaten away from rust caused by muck settling in the bottom u bolt cradle of the stock setup.