I am a 1994 S-10 with a factory tach. Most of the gauges are not working. I have a chance about buy a instrument panel out of a 1997 model that does not have the factory tach. Do you think gauges from the 97 model would work?

I would call a dealer but they should work. Ask the dealer first they should know. I don't see why they wouldn't though.
You should just have some extra connections