Upon the surrender of the outstanding bonds, the new bonds shall be issued ratably to the holders of the original outstanding bonds. Each holder of such original bonds shall be entitled to such proportion of the new bonds as the total amount of the principal and interest due him on his original bonds, upon the date of the recordation of the reassessment, bears to the total amount of the principal of the new bonds. In making distribution the legislative body may assign the different bonds and allot maturities in such manner as to it shall seem equitable.