switching bumpers
In the back you need a '70-72 Duster bumper and mounts. One of the mounting holes for the earlier brackets just needs to be drilled, piece of cake. The other is a little more complicated because the mounting hole needs to be near the middle of the much larger hole where the shock bumper goes through the rear crossmember. There's a couple of solutions, depending on your skills. If you have access to a welder, you can just weld a flat plate into the crossmember to fill the shock mount hole. If you don't have access to a welder you can make a bracket that mounts to the frame where the original shock mount bolted in and goes out to locate the 70-72 bracket.
Here's a "how to" on what I did with my '74 Duster to convert it to the earlier bumper style...http://www.forabodiesonly.com/mopar/showpost.php?p=1970342487&postcount=70
Before and after...
In the front you would also need to use a Duster bumper because the Dart uses a lower valance. But there are some differences with the nose of the car, so I'm really not sure how well it would work. I cheated, I installed an entire '71 Dart front clip to change my car over to look like a '71 Demon.
In the back you need a '70-72 Duster bumper and mounts. One of the mounting holes for the earlier brackets just needs to be drilled, piece of cake. The other is a little more complicated because the mounting hole needs to be near the middle of the much larger hole where the shock bumper goes through the rear crossmember. There's a couple of solutions, depending on your skills. If you have access to a welder, you can just weld a flat plate into the crossmember to fill the shock mount hole. If you don't have access to a welder you can make a bracket that mounts to the frame where the original shock mount bolted in and goes out to locate the 70-72 bracket.
Here's a "how to" on what I did with my '74 Duster to convert it to the earlier bumper style...http://www.forabodiesonly.com/mopar/showpost.php?p=1970342487&postcount=70
Before and after...
In the front you would also need to use a Duster bumper because the Dart uses a lower valance. But there are some differences with the nose of the car, so I'm really not sure how well it would work. I cheated, I installed an entire '71 Dart front clip to change my car over to look like a '71 Demon.