I think that if you disable the EGR system and air recirculation system you'll hit the major items. That can be as simple as blocking the vacuum lines to these devices. The electronics and vacuum switches can stay in place with no ill effect.

I'm pretty sure there is no electronic control of the vacuum singal to the transmission.

I don't know if there's any benefit to fitting the other style air cleaner in place of the remote air cleaner used in trap oxider applications. You have removed the trap oxidizer, right?

I think the California versions of the 85 300D and 300SD had different transmission gearing. That will require a replacement transmission to un-California-ize.

Sixto
91 300SE
87 300SDL
83 300SD