68 Fury drum to disc conversion

I am in the process of converting the front to discs. I have spindles and 2 piece rotors off of a 72 fury.

Are the 2 piece rotors interchangeable with the one piece rotors?

It seems the 73 spindle is preferred? Why is this? What changed in 73? Is it one year only?

Are all control arms and other suspension components the same? I do not have control arms off the car but still have access to them. I will likely rebuild control arms at this time as well so if the 68’s are the same I will...

68 Fury drum to disc conversion