Is it possible that a 1973 A body K member

1970Duster said
If you want to run the 73 k member you'll need the LCA from the 73+ in order for you to bolt the sway bar up. If I'm not mistaken you'll also need the steering linkage to from the 73+ as well. You can use the 70 brakes, spindle and 70 UCA, if you don't want to convert to the BBP

No, you can use the whole package off a 72 back K-Frame on a 73 up K-Frame. This is a common swap off a /6 or V8 pre 73 when you want to use a later spool V8 type K-Frame.