I get them from the unit database:
http://direct.faforever.com/faf/unitsDB/
select a unit (for example UEF T2 engy), when clicked it loads the unit detail page:
http://direct.faforever.com/faf/unitsDB/?id=UEL0208
look at the top where it says UEL0208
if you click this part you get the unit blue print
in this you can see unit categories etc
you can do this for each unit, then its just a case of finding which categories will uniquely identify your unit and exclude all others