Some 93 Formula Woes

So I got a 93 formula firebird. Been fixing it up and I found a cluster guage out of a 95' F-bird with only 5K mile difference so I purchased it. I thought mine was bad because the oil pressure needle was bouncing all over the place with no consistancy. I put the one from the 95' in my 93' and now the oil needle is doing the same thing but the RPM needle drops when I give it more gas ..what in the world is going on ? I will be crusing at 40-50mph and the rpm needle drops to 0 but as soon as I stop it goes up to 700rpm and holds for idle. Any thoughts ?

Also the oil pressure needle has me mildly concerned that my engine is being starved of oil or is this a possibility of a faulty pressure sensor ? When I cold start the oil p-needle jumps to 1/2 way and then when I rev or drive it drops down to almost 0. There is no clicking/knocking coming from the engine that I can hear so am I being teased by the sensor ? a circuit ? any thoughts on this as well would help.

Ok if you can take the oil sen wire off the sensor. turn the key on without starting the motor. (It should be pegged to the max) One other thing is to check the wire for damage that will also make it erratice. check to see what the gage is at when the egnine is not running when you reconnect it. should stick at 0. check and see if the oil sensor is leaking oil thats another reason it would act up.