I know it would be alot easier to put a 70-72 duster front end on your 74, that just requires a different hood, grill, bumper and bumper brackets. Dodge dart/demon front fenders are different from plymouth, the wheel opening lips dip in on dodge and the flare out with plymouth. As far as the dodge hood and fenders bolting up to a duster.....i have no clue but I would put money on running into fitting problems.