compession with after market pistons

ok pistons have 40 stamped on top the #405p are on the side/ press pins. but the rods all have3418645 on one side of the rod.But differant # on the other side/ differant type or stamping on more that one or two. one rod has on it big type WDF . now it,s a fact finding goal. need batterys will post pic,s soon. als