I've gone from a '73-'74 to a '75-'76 a while ago but don't recall all the specifics. It is easier than your conversion will be. You have to have the corresponding '73-'74 bezels to go with the grille. But there may be an issue filling the gap between the grille and the bumper. It has a filler that earlier models don't because it sticks out more with the shock absorber bumper brackets. It might be possible to incorporate it somehow unless you collapse the bumpers enough. There may be some fabrication involved if you swap over to a standard bracket bumper.