GM spindles & hubs come in two styles. But the 73-91 GM knuckles only come in one style. They fit on pretty much any ball-joint D44 (I use the GM outers on Ford & Jeep Danas, too). You’ll need flat top knuckles to run a crossover drag-link...casting #C36519 & #C36520. Here’s a pic of the pass side flat-top next to a round top knuckle...
Also, either style GM spindle & hub will bolt up to any GM knuckle. But each style spindle needs the correct hub. (It’s really not as confusing as it sounds). So you can run either small or large bearing spindles & hubs. And the THORparts hubs are available in either style. The smalls are somewhat harder to find but not “rare”.
Lastly, all of this stuff interchanges with the Corp 10-bolt too. However they never came with flat-tops. So you will need to run D44 flat-tops on your 10b axle to use cross-over steering.