The last 242ci 4.0L I6 used in Jeeps up to 2006 was a direct descendant of the seven main bearing 232ci 3.8L I6 that came out in 1964. IMO it was the best mass produced I6 ever made. The fact that it lasted 52 years is testament to just how good it was.
Through 1965, the standard engine in the American was a flathead 196ci I6, it was the last flathead engine on the market. This car, equipped with the 3-speed manual transmission with overdrive, was the champion in the Mobil Economy Runs and was considered a VW fighter. The OHV 232 was optional in the American from 1965 on, but a smaller displacement OHV 199ci 3.3 L version of the same engine was standard from 1966 on. I had a couple of Americans back in the day. They were sturdy/reliable/durable cars and were inexpensive to purchase, maintain, and repair. But, they had rust problems wherever salt was used in the winter. I had to retire both of mine due to rust, but the engines still ran well. Besides the engine, the two things that stand out in my memory are the reclining front seat backs, and the excellent heaters. They were highly regarded cheap winter beaters when I was in high school.