There is a cross member on my '61D200, '68 D100
and '65 D100 that "drops" under the drive shaft.
It is, in the general location, where you'd put
your t-case cross member. If your frame has this
member.... it'll likely have to be removed. There
are 2 brackets & 8 bolts per side needed to hang
that NP201 cross member.
John