Assume for a moment that WDWRR was standard gauge. What kind of speed could those engines attain with the governors removed?
Also, considering they were rebuilt by The Disney guys in Tampa, wouldn't they NOT have Baldwin boiler plates but rather something like
Disney Locomotive Works Tampa FL. instead?

I think you would find a greater number of responses to this interesting thought, over at the group listed below. It seems to be a bit of speculation in the fuzzy area - not so much a rail preservation question.
http://finance.groups.yahoo.com/group/parktrains

Steam locomotives don't have governors. The Yucatan locos were run fairly regularly at 30 mph when in service in Mexico...guage doesn't enter the equation, driver diameter and cylinder size does.