(i was gonna post this last nite but my net connection died - so here it is)
shouldn't matter, although if you are concerned you can hook up the 2nd output on the thermo switch into a relay, to then power your dash guage. if your guage needs a 12volt rail, u should use a relay to minimize the possibility of any resistance. also the ecu should be powered from elsewhere, rather than directly from the water temp switch so it shouldnt be a worry.
this website has lots of demonstration relay setups. very handy for the interested garage sparky. (who doesnt have a welder)
http://www.the12volt.com/relays/relays.asp