I personally ran a 2.9 (yes i know its not a lima) well into 300,000 mile territory. There was another guy here many years ago had 660,000 on a 87 BII with a 2.9.
This is important because the general consesus is the 2.9 is junk.
But basically, any engine (except for a few chrysler products) will go insane amounts of miles if you keep oil in them and keep them cool.
However, ive always heard (and kind of experenced) smaller engines last longer then bigger ones. The lifespan of a 2.3 is generally gonna be much greater then that of a 460.