What all do I need

If your car is the 73 Duster listed in your signature the housing needs to be 52-5/8" wide. That's just the housing width, not the total width. And the spring perches need to welded 43" on center with the pinion a couple degrees down (that figure can vary some depending on the application such as a race car vs street car vs. street/strip car). The axles in the Summit listing are decent. Not a race axle but plenty for a street/strip car. I see their listed as 28" wide where-as stock axles are 27-11/16". To use them you probably need to use green bearings and take out the thrust pin (clutch type SG) or thrust block (open carrier or cone type SG). You will also need to use B or E body brakes. They also do not have bolt access holes which makes it a little rougher installing them. If you want direct bolt in axles look on Moser's website. They have a low cost axle for no more than the Summit axles that are set up to be used with what ever brake size you have (there are 3 or 4 options that you pick from). And I believe they have the access holes which believe me you want.