A pic of the brakes/spindles would be the most helpful, we can imagine the control arms were most most-likely built to use the ball joints that were stock for those.
Probably yours will be one of two kinds: '72-down A-body (Chevelle etc.) is a specific application that will cover a lot of possibilities, and '73-up A (Malibu etc.) will cover the others. The differences between the two will show up in the diameter of the lower cup (where it presses in, only a small difference but important) and the taper angle of the stud. I would bring your spindles/uprights to a parts store and have a counter guy lay out lower joints from the two GM applications and see which studs fit snugly without wiggling around, thereby signifying the taper angle is correct, and have a calipers handy to compare cup diameters...and then buy the matching upper joints, checking again that the taper angles feel correct.