Ben....true, & good points. But like you said above, it has the correct 516 bumper, plus a 13" Heritage head isn't going to activate the speed switch on a 516. So it can't be a Heritage head. What I think is more likely is that the air adjusting plate & belt decal were either ordered new for a Legend II & fitted onto a 516, or they were used parts taken from a Legend II in some dealer's trade-in pile.
Rob