i dont know Mach maybe its the 11 years as a mechanic that gave me that logic. you try lining up a cylinder head gasket when you put that 40 pound cast iron head on while leaning over the fender.
they(car manufacturors) put them there for a reason so maybe that is my logic. you may have had success without them, but we tend not let the "backyard" mechanic to lay down the rules. yes you probably can line it up without them, but why would you? if you where in a pinch and the car had to be done, i would try to make a dowel out of something first before i was ever to bolt the head on. as for shifting side to side, i think so, but i am not sure on that part. Chris, you have built more engines than you can shake a stick at, why dont you give a poke at this?
Big Bopper,
USE THE DOWELS!!