The only thing I can think of is the details.
Not just fluff. But "standard equipment" in the 1880s and the details of steam vs. electricity vs. diesel are different.
That's not to say SotC couldn't (or shouldn't) be used. Just that its not quite just a matter of changing the date and the flavor text.
I am guessing you haven't seen SotC then.
It would take 15 minutes to mod.
Josh is right here, the system for SotC is more abstract than Steam vs. Electricity and equipment lists. The only equipment list in SotC is an abstract of how much things tend to cost, and the only equipment you ever care about is the stuff that gives you bonuses. As far as the game is concerned, a gun is a gun is a gun, unless THIS gun is special. A car is a car is a car, unless THIS car is special.
If you're interested, the SRD for Spirit of the Century is available online for free at
http://www.faterpg.com/dl/sotc-srd.html. Take a look at it, and if you still want to debate about the merits of the system for Steampunk then you can do so with some knowledge.
