Hi there,
I know there was a product recall on some Mag 30 forks due to the crown cracking, Mag 20/21 crown/steerer should work.
The steerer is 220mm from the bottom of the crown to the top of the tube. there is 197mm of tube from the bottom of the bearing to the top and 50mm of thread, the clamps are 1 inch.
Many thanks
Cliff