I noticed in L&E (p 148) it lists the number of special abilities an undead creature can have as 2d6-7, for a max of 5. However, in ACKS Core (p 123) under the rules for ritual Necromancy, the number of special abilities a character can create intelligent undead with is limited to 1+Int, which with a maximum of 18 Int for a +3 bonus would only amount to 4 special abilities. I have checked the errata and found nothing to settle this apparent discrepancy, which has lead me to a few possible conclusions.
Option 1: Unintelligent undead raised through a spell can have up to 5 specials, while intelligent undead are limited to 4 (this would seem to imply that intelligence is weighted similarly to a single special ability). Mechanically feasible, but seems lacking in flavor - generally I would think of intelligent undead being both more competent and more powerful.
Option 2: The spell vigor can grant +1d3 Str up to a maximum of 19 for a +4 Str bonus. A custom spell could be researched to grant +1d3 Int up to 19 for an indefinite duration (or perhaps a daily duration reapplied each day) to allow a character to artificially boost their Int for the purposes of Magic Research. This has interesting implications on why every caster hasn't already researched this spell.
Option 3: I misinterpreted something and have no idea what I'm talking about.