AMC was not involved in the 230 at all. Kaiser Jeep owned Jeep until 1970 or so...AFTER the 230 came and went.
Kaiser did use the civilian version of the 230 from 1963 to 1965 in the Universal series and the Full Size Jeeps. Then they redesigned it and used it from in the M715 family, correctly called the G890 series, from 1966 (prototypes) to 1969 (Possibly early 1970).

There were no other engines or transmissions used in the stock M715 trucks other than the modified for the military truck 230's.

There has been talk over the decades here at the Zone about the different input shafts needed to swap other engines in and mate to the stock trans and the T18 vs T98 diffewrences as well. We have been told uin years past the the 304 and 360 AMC have been mated to the T98 by swapping input shafts, bellhousings and adding a spacer...so I knew it has been done...just had never seen one.

I am extremely confident that someone did this with your truck...found the components and swapped the stock setup to a less troublesome, more common engine.

Its not a bad thing...would have been interesting if such a thing had been done factory...maybe they would have lived longer...

To me, the 230 is just another of the "Wow...what is that?" things about the M715 that make it desirable to some people....like me for example...but nothing wrong with yours...I love seeing all the variety and possibilities...THAT is a big reason we ever got started right there!!