I got a 69 chevelle with no electrical and I will be replacing all the wiring soon. My question is...is there a way I can test the gauges to see whether or not they work, so I can either buy new ones?

Well, let's see....you could do them individually

Volts: easy, just need 12v and ground

Oil: 12v, ground and a running engine or oil pressure apparatus to create pressure with a stock style sender and sender wire.

Fuel: 12v, ground and a ground lead from a grounded sending unit...in the car or out, if in the car you want some fuel to make sure it's working since it will read that amount of fuel.

Water temp: 12v, ground and stock style temp sender w/wire...you could use a pot of boiling water and the sender bottom in it for this.

Tach: this one might be a little trickier....may have to find another running vehicle and test it that way, including the 12v and ground wires.

Speedometer: 12v and ground, maybe use a drill to spin the speedometer cable connected to it to simulate the car moving?

This is going to take some effort on your part, regardless. Good luck!

Very nice explanation Mike. I started a reply to this post and it went from bad to worse so I backed out.

Mike, thank you. I will try those suggestions out.