350 vortec temperature gague

[farmero]

I put a 350 vortec in my 79 Duallie (New GM replacement), now I need to straighten out the temp gague. I have a manual temp gague connected to the cylinder head. This gague fluctuates from 190 to 300 depending on how I use the throttle. Is this flucation normal? I have a stock electrical temp gague in the dash that I would like to hook up. So far I can't find the wire for it. Also, which sending unit do I need? I know this truck does not have the original dash cluster in it, so does that make a difference? Also, what color wire should the tack have to the dist? Happy New Year to All.