Wolfgang's post sounds a little complicated.
Larry' is a little more on the mark. Just install one or more "T's" where the original temp/pressure senders install (right next to the distributor) to handle whatever senders you have and Git R Dun!
I didn't bother with any of that. I used the original Vintage style multi-gauge with the temp scale on the top, then bought a dip stick thermometer to find out what temp the engine is really at, then drew a red line on the face of the gauge with a Sharpie to show me 205F degrees (where mine runs when it's hot) and that's that.