When considering low-buck performance for a Mopar, good power potential and ready availability make the 360 a winner. However, the days of buying a good used but serviceable LA-series 360 to swap are drawing to a close, and even good cores are getting harder to find these days.
The later Magnum-series engines open the door for a number of possibilities. It isn't a problem to find a decent used 5.9 Magnum engine from late-model used-parts sources, ripe for whatever performance plans you might have. In fact, Magnum mills seem to have survived the rigors of service much better than the earlier engines, owing to improvements like a better ring pack with thinner moly rings and effective MPI fuel injection with modern engine management, all leading to a reduction in bore wear. It's not uncommon to pop the lids on a 100,000-plus-mile Magnum and discover negligible bore wear, while the older carbureted small-blocks would have been spent. Good bores and a sound engine are essential to the foundation of a low-buck performance engine.
...the 300hp version is the same engine as in your typical Durango, van, or Ramtruck. With the 300hp crate you get a bone-stock production bottom end, complete with the stock truck pistons and cam. Changes are only the addition of a center-sump passenger-car oil pan, an LA engine-style front cover, a conventional distributor, and a two-plane carbureted intake to replace the factory "beer-barrel" MPI injection system.