Lords of Olympus specifically states that there are no equivalents of Intelligence or Charisma (as those are to be role-played), so we can drop those from ability score conversion. That leaves four ability scores to four Primary Abilities. Simple, right?
Not quite. Let's see why:
MIGHT and ImmortalsMight is clearly described as physical strength in Lords of Olympus, so that means Strength in Wrath of the Immortals (WOTI). I have some minor doubts, as WOTI also has a table that shows that damage from bare-handed attacks is based on Immortal rank.
A stunning range of 2d6 to 4d6 damage! Well, I think I'll stick to the conversion of WOTI STR to Lords of Olympus MIGHT. However, if your Immortal level is from the Empyreal to Hierarch range, you are definitely among the top in your class; those below that range are considered Tied in their class ranking.
So: MIGHT is based on the Ability Score conversion table.
FORTITUDE and ImmortalsWe don't follow the same rule with Constitution. According to the table above, and other text in WOTI, hit points are determined by your Immortal level WITHOUT any influence by Constitution! Therefore, an immortal's level determines the FORTITUDE class ranking in Lords of Olympus.
Constitution only impacts an Immortal's ability to resist Immortal poisons. Regular poisons, as you might guess, don't affect immortals. Therefore, we ignore the Constitution ability score as negligible for the purposes of this conversion and use the table that I created for translating Immortal power levels into Lords of Olympus class rankings (which I thought was a mistake).