SBP DISC to LBP DISC SWAP- 72 Swinger

For the OP, 72blunblu covered the upper situation. You'll need to run a bbj upper control arm (73-76 A body) or sleeve on your existing arms.

The bumpsteer thing is so overblown it's crazy. I run nothing but the FMJ on my a-body cars anymore. Never broken a ball joint or had bumpsteer. Look on the tech pages at Big Block Dart for the write up regarding the issue.