It’s generally accepted that most 450s with the petrol engine will need an engine rebuild at least once in its life, usually around or after the 50,000-70,000 mile mark.
You’ll know your engine needs a rebuild because it’ll drink oil like a Mazda rotary then eventually begin misfiring due to low compression.
It seems to be caused by a combination of how sensitive the engine is and poor maintenance. A well maintained 450 engine shouldn’t require a rebuild, though it can still happen.
Whereas a 451 engine *could* be okay going say, 20k between an oil change (don’t ask how I know), a 450 engine will likely wear out much much faster doing something like that.
It seems like the best preventative measure is anal maintenance. Change the oil on time, change the plugs on time, don’t abuse the engine, and so on. Age may also become a factor too as these cars continue to get older. However, when buying secondhand, you don’t really know how well the PO adhered to a maintenance schedule.