To make the chrome bumper look right you'll need 71-2 fenders, the 71-72 fender trim, the bumper (of course) the bumper mounts which are reproduced, the fender fillers, the proper grill, the lower valance, the lower turn signal parking lights and the one part that is not reproduced-the plate that fits between the bumper mounts and the bumper. This part can be found used on occasion. I believe you could make a substitute (I actually made a cardboard pattern off of one) but it would not be original and therefore the crashworthiness would be unknown.
I encourage you to price all the necessary parts as this conversion is not cheap to do right.
It is possible to fit one without the fender change, but it will have to be mounted about an inch and a half lower than the normal position and will look a bit off to the trained eye.