Below is a chart containing the distribution of player castable base spells in loot. This list does not include item spells, or cantrips (minor, major, epic), and is meant to assist in the creation of a suit of armor for an item only template.
How spells land on multi-slot armor
Any spell that comes on a slot listed can show up on multi-slot armor that has the same coverage. For instance, since Strength comes on a breastplate, it can also show up on a cuirass, hauberk, coat, or shirt.
The only exception to this rule is for the abdomen. If a spell comes on the abdomen slot, but not on the upper or lower legs it is considered an upper body spell, and will not show up on 3 piece leggings.