Just be careful; at one time, International had its own 401, which is
a big, heavy monster. IH called the AMC 401 a "V400", to distinguish
it from their own engine. The article on the Scout in Wikipedia
states that "some 73/74 pickups and Travelalls received the AMC
engine due to a shortage of IH V-392 engines." IH already had a
contract with AMC to use the 258 in their light trucks (including
Travelalls and Scouts), so the 401 was presumably an extension of
that agreement. The IH 401s were supplied with a 2-V carburetor and
manifold.
IH was a leading supplier of cab & chassis units to the school bus
and motor home markets, so it may be possible to find 401s powering
those vehicles.
--Glen