Most all the newer speedos are electrionic, but a simple pulse generator will usually be all you need to make them work. If you have cruise, that generator can run some speedos.

The gas gauge, and voltmeter are simple in most cases, but the engine gauges can be difficult, most cars in the 90's and newer no longer have seperate sending units on the engine, but use outputs from the computer to run the gauges. So to make them work, you will need an interface to change the digital signal to analog.

Tachs can be fooled with a chip for use with a V8.