I had a '65 American, no doubt they get looks... The '59 Super 6 would have the 195.6" engine, if it's got some problems, a swap could be cheaper than a rebuild but rebuild parts can be obtained if you wished to go that route. However, in 1963 AMC introduced the 232 I6, a very stout engine, much better than the Nash design 195.6" ( 196" in all common respects ) which dates back to the 1930's. You can use a pre 1970 232 and it will bolt right in. Then you have more modern hp and more modern reliability. 232 turned into the 4.0L Jeep engine we know today
The 196 needs it's valves adjusted every other oil change approx, and head torqued every other oil change. They can be dead reliable but you do need to take care of them.