73+ disc swap balljoint.

I've bought the last bit of parts for my disc conversion/ supsension refresh on my 70 dart. I bought new lower balljoints for a 75 dart along with everything else because the disc spindles came from a 75. But I went to mock everything up this evening and the lower balljoints I got won't fit. The bolt holes are too small on both balljoints. And the knuckles are different lengths! I assume they are both supposed to be the same length from left to right or else steering would be wacky. Oreillys is closed now for the holidays so I can't return them just yet.

But just to be clear. I do need lower balljoints from the donor car, not for a 70 dart. Correct? And why wouldn't the bolts fit through the balljoints? I'm not sure what vehicle the balljoints are for.