I dont believe so, but you can just convert the 6-lug hub to 8-lug. Im assuming its the front axle you are talking about. If thats the case, all you need is to find a 3/4 ton chevy truck with a d44 or 10 bolt in the front that is 8-lug (the junkyard is the best place to find this). Then just remove the hub/rotor assembly, and the brake backing plates. Then just install them on the blazer with the 1/2ton locking hubs, and wallah you have a 3/4 ton 8-lug front end.
-Harrison