I pulled the mystery 350 sbc out of my 79 k10, and took it apart. Pulled the oil pan, Its a 2 bolt main motor, 3970010 on the rear. Has been rebuilt for sure, rods marked .010" oversized, looks clean. Was told that the engine came out of a dirt track car, has a very mild lopey cam, Tarantula single plane intake, etc.. I'm trying to identify what kind of balancer is on this thing, maybe someone could help identify it? Ive had 2 people say it looks like a 283 balancer. Also note the aluminum spacer used on the water pump, not sure why? Any help is greatly appreciated!