A Body Disc Brake Swap 101

Will any a body UCA (drum or disc) from a 73-76 work for the disc swap? I keep reading that I need the disc brake 73-76 UCA's for the larger balljoint. Do the factory drum brake UCA's 73-76 have the small or large balljoint? I just picked up a 73 Duster with drums up front. I already have an extra set of disc spindles/calipers/rotors. Just wondering if I have everything I need or if I need to find a set of 73-76 disc UCA's