My speedo and battery charge gauge work fine. The Tach, fuel, oil dont work. Does this sound electrical or the gauges themselves are broken? Should I buy a voltmeter and test the power to each of the gauges?

Have you downloaded the factory service manual from the link I posted in your other thread? You really need it based on the questions you ask. There are troubleshooting procedures for everything on the car in it.

After I got the car running good, I noticed that all the gauges except for the tach and clock were working. I changed the tach for another one and it still didnt work. I have followed the wiring and they seem to be intact and plugged in. I bought all new fuses and replaced all of them. now nothing but the battery charge works. what could be going on?

The manual you can download will most likely have your answer.