yes stock crankshafts are very strong and very reliable, i have yet to hear of one breaking, more likey u bend a rod or burn a valve first , balancing is important in making sure everythign spins evenly when the crankshaft is rotating and the pistons are going up and down, if u dont balance the engine properly stuff will begin warping and breaking once higher rpms are reached, and things begin blowing out, like ur crankshaft seal.
no idea about the gsr rod question