I have not seen this thread before so I apologize for jumping in late. I like the idea of replacing the leaf springs in the tube with a solid bar to be used as a anti-sway bar. I am no expert on sway bars but is seems like
two one inch bars will make it super stiff. You may decide that one bar is plenty. Usually stiff bars are 1 3/4 are used and they have diagonal arms that attach to the A arm on newer cars which provide a lot more leverage to twist the large bar. Have you done anything to stiffen the roll of the rear of the bus? It seems that a lot of anti-roll in the front will cause serious oversteer. Just my two cents, can't wait to hear how it turns out.
Mike