Found this on a briggs web page
Type of Push Rod Based on Engine:
Single Cylinder OHV - Model Series 260700, 261700 upper push rod (exhaust) is hollow. Model Series 28N700, 28Q700, 28U700, 28W700, 287707, 310700, 312700, 313700 exhaust push rod has a red band of paint for identification and is steel.
Intek V-Twin OHV - Intake push rods are aluminum.
Vanguard V-Twin - All models (except 540000, 610000) exhaust valve push rods are aluminum. Model Series 540000 and 610000, all push rods aluminum.