Upgrade Path Question

[aokces]

How can unit upgrade paths be edited (for example changing it so that rifleman => alpine)? Or is it hard set based on location in the unit graphic file? Thanks

 

[Mercator]

Unit A upgrades to unit B if they're of the same unit type (I think), and unit A goes obsolete with the same tech as the prerequisite for B... And Civ2 prefers upgrading either to a unit lower down in the rules, or with better stats.

That's the general idea anyway. I'm pretty sure there's some more trickiness going on, but I can't remember the details of that... Beware of the Knight and Musketeer slots.