A 71-72 bumper can be put on any 67-72 But you must use 71-72 outer bumper brackets because they are longer in order to clear the parking lights in the bumper.
We carry the 71-72 Clear park light lenses you'll find them here on our site.
http://www.gmcpauls.com/SALE_SPECIALS.htm
They are currently on a sale for in a kit on that page for $20.00 which gives you a Left & Right lens, 2- lens gaskets, 2- Amber 1157 bulbs & 8 stainless steel mounting screws.
GMCPaul