New disc axle installed, do I really need to change the MC and booster?

[mgchevyparts]

You'll be fine. The things to check with a drum master:1) front brakes drag=internal residual pressure valve, can be removed if present. Yours doesn't have one as they are not dragging. 2) smaller reservoirs of drum brake master will require topping off fluid in the future as the pads wear out, this is due to the disc pistons being much larger then drum cylinders, just top off as necessary.
Line diameter makes no difference.
As you found out every thing works.