Dodge Demon ball joint question
Lower will fit the lower arm regardless. If you are certain it's a 73 "stock" conversion, and not some aftermarket deal, then you have it right.........buy parts for the 73 WITH disc brakes.
BUT be careful with 4 items.........the steering box, pitman, idler, and center link.
You could have either setup depending on what steering box you have
Here:
http://www.forabodiesonly.com/mopar/showthread.php?t=236925