Is summer school getting to you tommy?

Could the frame break somewhere around the mount? Sure
But after having done a set of James duff arms before and seeing them last fine for the last 4 years I doubt tommy will have much problem.

Reasons for not boxing the frame:
Save time and money of doing it right
In nearly every Ford frame I've seen boxed, and no cage, it ends up cracked on the edge where the boxing ends or begins. C channel frame like these are designed to have a certain amount of flex and by strengthening adds stress to the adjacent areas.

Reason for no crossmember:
Time, money, added hang down

Is this axle swap koh worthy? Not yet