Somebody correct me if Im wrong, but I know for a fact stock Blaster wheels are 8" in diameter. So, as long as the last digit in the tire size is an 8, they should work. Only thing about an 8x8 tire is that they are much narrower than the more common 10" wide rear tires that many people run.
These smaller 8x8 tires will probably work, but you will have less tread in contact with the ground and traction may suffer at times.