hi ed,
 
they were actually stapled with "magical metal-penetrating staples" from 
the factory, and flap inboard as well towards the engine, over the control 
arms.
 
i have several original examples if you'd like to see.
 
as a replacement, i acquired at first [from year one] the GM a-body 
counterpart, cut them to pattern size for the 57-9-  the trick to look 
original is to remove the original staples, and from behind, with a thick sewing 
needle, puncture the new flap in the same spots the staples penetrated the steel 
inner fender- then use 18awg solid copper wire and make little sutures that 
appear as staples, twist them or fold them facing the wheel- then with a 
permanent black marker- give them a little hit to tone down the copper 
color.
 
this can be done with cheaper materials as well- like generic sheets of 
rubber steam-fitters' gasket material