The kit you bought is made for '65-'72 A bodies with 10" drum brakes. You have B body spindles on a '73 A body. Of course they're not going to fit. You need to either get the kit for the appropriate year B body spindles that you're using (are they disc or drum spindles? They're all different), or convert to the earlier A body spindles- but that would mean your new QA1 upper control arms have to go. They have the large upper ball joint, and the A body spindles for that Wilwood kit take a small upper ball joint.
Even if you somehow made the caliper brackets fit those spindles, you'll find the wheel bearings are a different size.
See if you can still exchange it for the correct kit.
Edit: I *believe* the kit you need is
1975 DODGE CHARGER Wilwood Disc Brakes 140-15465 Wilwood Forged Dynalite Pro Series Front Disc Brake Kits | Summit Racing , since those are B body disc brake spindles you have.
