Disc brake conversion 67 Dart

The 9 and 10 inch drum brakes both used the smaller upper ball joint.
The disc brake spindles use a larger ball joint. Its larger on both ends.
Recently someone produced tapered bushings that would fill the void between the smaller ball joints stem and the hole in the disc brake spindle.
That would allow keeping the same upper arms and small ball joints you have now. I have not used those tapered bushings , nor have I read any feedback related to their use so I can't say if they are safe.
I do know morse tapers are used in machine tooling and resistance welding tips and when they are properly machined they stick together very well.