Magnums were an improvement over the LA's. Metric and fuel injection needed to happen. There are some good things that happened:
"Introduced back in 1992, the 5.9L Magnum was the successor to Mopar's successful LA-series 360. With improved cylinder heads, better sealing, higher compression, thinner rings, and an all-new higher ratio valvetrain among the many modifications, the 5.9 Magnum breathed new life in the old small-block V-8. The revision extended the service of the traditional Mopar small-block another 12 years, finally ending production with the 2003 model year. The 5.9 was strictly a truck engine, powering the likes of Durangos, Dakotas, Rams, vans, and Jeeps. Although not a muscle car engine in the traditional sense, power ratings were between 230 and 250 net horsepower depending upon year and application, up from the last LA-series 360's 190 hp.
With a long production run as the last Mopar small-block, these Magnum engines are stacked up like cordwood in boneyards across the country. As pretty much a direct bolt-in for any classic Mopar muscle car or truck, a used 5.9 is an easy and cheap way to up-power your Mopar. We find these truck engines tend to survive very well, often with minimal bore wear owing to the factory 1/16-inch moly compression rings, tall overdrive gears, and the port fuel injection system. The short-blocks more often than not can be freshened with little more than a set of rings, bearings, and gaskets, and sometimes they are good enough to run right out of the boneyard."
The Motor Trend article went on to say the downfall was the head cracking issue and followed up with mention of the Engine Quest heads being a good fix for the problem.
