Welcome to the forum, maystre.
I don’t know if that’s possible with Hasbro 1998 CD, unfortunately.
In case you want to give TripleA a try instead, this is how it works there:
For doing this you need to edit the respective map xml-file.
Inside the ‘mapname.zip’ you find the directory ‘mapname’ and inside this directory there is the directory ‘map’, that apart from others contains the directory ‘games’.
Open the xml file of the map you want to alter with the editor (don’t use Windows notepad for this task) of your choice.
Search for “territoryAttachment” of the countries you want to change and adjust “production” according to your needs.
HTH :-)