Color conversion chart? (Specifically for gun metal)

Currently painting Tamiya's Alfa Romeo 155 Jagermeister. I noticed that there're a lot of parts on the exterior painted Tamiya X-10 gun metal. I'm in a rush to finish this and would like to minimize the trips to the store to pick up all these colors, however, so I was wondering if Gunze's Mr Color 61 Burnt Iron or Gunze Aqueous H28 Metal Black are good alternatives.

Are there any color conversion charts for the various paint brands on the web somewhere?

Hope this help.

http://www.airmodel.sk/indns_eng.html

You may find this chart useful too:
http://www.thehobbybarn.com/resources/paint/humbrol_color_conversion_chart.htm

Gainsbourg, thanks for posting that link there, it is great and very useful(came at just the right time for my next project too)

Ray