Since your scamp is a 73 the upper control arms will already have the larger ball joints. So all you need is the spindles. Take a look over at bigblockdart.com in there tech section there is a great article on using spindles from B,F,J,M,R body cars will work. I took a set off an 85 5th Ave. There are ton's of those in the junk yards.
After 73 Chrysler used a lot of standard parts on all there cars...made it cheaper..
Take a read and swap away
Cheers