I "think" a 71 fender would fit (one w/o the gills) but due to the differences in the grilles there might be some issues in that area (which might be what you are seeing). 72-74 fenders would bolt up but the marker lights are completely different whereas I believe the 70 and 71 used the same marker lights.
Generally, there is a lot of adjustment in the fenders, your issue with the grille might be a result of the fender adjustment. The antenna hole can be worked with/around if necessary.