318 and 360 small block question

Seems reliability is more important to you than power, if that’s the case either can be built similarly for very good reliability. Although you can have your cake and eat it too, junkyards are full of 5.9 magnum engines and they have a few benefits over the La for reliability. Hydraulic Roller cam, thin ring packs, hypereutectic pistons, just to name a few. Don’t overlook the 5.2 magnum either. They are more plentiful than the 5.9 and almost as good. Slightly less hp/Tq but same reliability.