A 4240 is probably one of the more under-valued tractors out there right now.
We bought one in 1990 with about 4000 hours- it now has 15000. Engine was rebuilt at 12000+- we had an employee who went on to JD tech, and he rebuilt her as a project. When he rebuilt it, we installed a 4440 head and turbo. This woke her up a little, but we left on a rotary pump at the traditional setting.
The naturally aspirated 466 is a very durable engine. It will take some fuel, but they are very dependable. Transmissions are also very durable. They are not built as heavy in the rear as a 44 series (4440, 4450), but are still a very good machine. I believe the rear end is the same, or very close, to that used in the 4430.
Best of luck.