Lt_Dan:
Sometimes you need patience. Not everyone visits here every day.
Yes, you can zinc plate die-cast carb bodies. Depending on your carbs particular mix of pot metals, you may be able to color chromate it w/out plating. If the zinc content is high, it may chromate well. If it's low, you'd need to plate it first.
Unless your carb was a shiny bright color to begin with, you may not want to use brightener. I tried to, and it was far too shiny:
I don't know anything about electroless nickle, but it sould be do-able.
Sean