Since I have three belted 375Mag magazine rifles and one flanged 375Mag double rifle i would choose the 404J.

Had a nice takedown English magazine 404J 30yrs ago. Have a barrel and some of the makings in the safe. Just haven't got there yet! May be cheaper just to buy one. Mmmm, and I have an action for a 505Gibbs sitting with a friend in the USA.