it is most likely a borg-warner tranny of some sort, although IH did make some of their own trannies back in the day. probably a closed knuckle D60 up front, and either a dana or IH corporate dropout rear. It might make sense to upgrade the axles to modern one tons if you can't get the brake parts any more.
Cool truck! All the IH's rusted out years ago around here.
edit:
www.binderbulletin.org is a great forum for the old corn binders