I only just noticed that TacOps errata v 3.02 addressed part of my question by taking the standard TechManual engine types off the table on page 308. So that much would seem to be settled already.
The question of how to distribute any applicable fighter item slots for the remaining types is still open, however. For instance, an Inner Sphere XXL engine supposedly takes up four slots on either a vehicle or a fighter. On a vehicle, those go to the body -- but how should they be split between wings and rear on a fighter, exactly?