Would like recommendations on a replacing the magazine follower for an Interarms MK X Whitworth 375 H&H

The one that came with it looks like it is for a standard action rather a long magnum action

Should the follower fill the magazine box?

Is it worth replacing the original spring?

My 375 and normal magnum followers in my MKXs are the same. I wouldn't replace an normal MKX spring.

I replaced my standard follower with a magnum follower (wisner?) from Brownells. I found it was wider than the Mark X and needed to be narrowed by a machinist friend. Works great now, but needs the extra step. Bob