[Question] Specialists Mages

How the game identifies that a wizard is a specialist one to provide its bonus and restrictions?

I made a test creating a Necromancer and there is no effect applied to it like I saw in every kit that I reverse-engineered.

Here's the problem: I want to make a wizard kit that's is actually a necromancer kit (from the Complete Necromancer Handbook). To do so my idea is to make a standard wizard and apply a kit on top of it with an effect that provides what a specialist usually gets (for better or for worst).

The problem is: the opcode that provides bonus vs school save is not IWDEE compatible (dammit, Beamdog, upgrade the damn thing) but specialists in IWDEE gets those bonus anyway, so it's not this opcode (346) that is used.

I know how to provide the extra spells per level, but IDK what to do with the spells restriction (banning Illusion and Enchantment as P&P) and save bonus (for self) and penalty (for others).

Can anyone give me a hand in this matter?

Thanks!