I wanted to see what i would need to do to install a tach on my 93 6.5l 5-speed 4x4. I am not sure if i have to install some type of throttle position sensor or what. I have a 4 wire -ground tach Im just not sure where on the truck it will recieve the rpm signal from since it has no coil or HEi.
Any info would be much appreciated!

The stock tach takes it signal from the alternator.

Tach's for diesels are a special breed.... a standard gasser tach will not work. As stated, the stock GM tachs take their signal from the alternator, but you can get a diesel tach that has it's own pickup, you glue a couple magnets to the balancer to give it a signal.....