The Subaru Sambar.
The Daihatsu Midget, the Mitsubishi Leo, and the Mazda K360 were all recent entries into the Japanese market for light trucks, and all had small displacement engines to take advantage of the Kei Jidosha laws, also all of these trucks has only three wheels (5 if you count the spare and steering wheel!).  Soon Subaru would place a four wheeled truck on the market, and all but the extremely cheap daihatsu would be replaced in an effort to compete.   The Sambar boasted four wheels over three, which allowed it to have a better ride, more stability and most importantly more space for cargo than any of the 3-wheelers could offer.  There was also a van version, and both were available with the 450 engine introduced that same year.  The early models were round dumpy vehicle and earned the nick-name "Hippo" early on.   For 1966 the sambar was revamped.  It gained new syling, a stronger engine, stronger frame, and more weight.
This is the early style sambar pickup, almost the same as the 1961 models except in small details.
In 1968 along with the subaru 360 sedan it would be imported to the U.S.A. officially.  Although some had been imported as early 1964. 
The 25hp engine that was available on the sedans as an option was also available on the Sambar line.  In 1973 the line was again restyled and gained water cooling.  Some of these models would also be imported into the U.S. for conversion to electric power by Jet Industries.   Of it's competitors from 1961 only one  was imported to the states, the cheap daihatsu midget was called tri-mobile and imported in the early sixties. 
Above left: The insides of the sambar truck.   Above left: Chrysler claims to have invented the minivan?  This is the post '66 style sambar van.
Sedan Back 450