I don't want to write a book but here goes
After market axles will work in all 3 carriers. 741 , 742 , 489. Green bearings the axles will not use bearing adjusters so the axles will have to be trimmed to fit if they are to long.
Also BBP axles when used you will need the BBp backing plates, BBp Drums, BBp park brake struts and BBp brakes,
If drilling your axles ? You need to put the fixture on the axle turn it clockwise until the lug hole in the fixture sees the large hole in the axle and mark the axle, then turn it counter clockwise until you see a lug hole in the axle and mark the axle. Move the fixture back until you are a the center of your marks. This is where you drill for the new studs. Drill and tap the axles for 1/2 20 race studs. This will leave more room for the holes to be drilled.
Remember when using your small bolt axles with BB wheels you will need to use 3/8 spacers to keep the tires from hitting the leaf springs.