Item.dec:
enchant_code_lnk & grade
Item.scp:
EnchantCodeLnk & Grade
Your pets also have a grade attached to them, same as the force core.
I'd recommend comparing some items of different grades and the cores used for them, this goes for both upgrade- & force cores as well as scrolls.
It should be fairly easy from here, if anything just ask.
A common approach would probably be turning both values into "12" and using that grade for your pets.