gauge help

[Big GMC truck]

I have a 1984 GMC k1500, 305, that is in need of some gauges. How hard would it be to put in a tach and a water gauge? How do I install the tach? Will the temp gauge come with a sending unit that will fit into the existing hole in the head.

 

[wildbilzrydn]

The only tachometers I've ever done are the sun supertach IIs and they're real simple, four wires 12 vdc(+), o vdc (-), 12 vdc from lighting system, and the signal wire from your HEI cap where it says "tach".
Temp senders i've done were mechanical, they come with a "bulb" that you thread into the hole where the Idiot light sender lives and a spring wound wire you push through the firewall and connect to the gauge.