62 GMC 3/4 ton Disc brake conversion

[69 customcamper]

I know this has been beat to death already. The info is a little more limited on the 3/4 ton. Has anybody managed to get late model spindles on the 3/4 ton? It looks like the lower arm ball joint configuration is the issue as the upper looks like you can bolt in the later upper ball joint to mount the disc brake spindle. I would rather retain the torsion bars if possible. But otherwise is everyone thinking the 73 and up crossmember is better? What is different from a 71-72 cross member VS a 73 and up?

Thanks!