upper control arms

I have a 66 valiant, im converting it to disc brakes. I have 84 new yorker spindles, and lower 67 balljoints. The top ball joint needs to be changed to the bigger ball joint. Im told that the upper control arm needs to b swapped out for a 73-76 dart a arm to keep the geometry correct. Im looking for a source for tubular upper control arms that are reasonable priced, or should i stay with the factory 73 an later arms? Any info will help, thanks