Lefnui

Hey this is my first post and ive searched everything i could think of on here and the internet in generalbut i cant find anything that talks about this. I have a 1980 rx7 with only 80,000 miles got it for just a 1000 dollars and it runs perfect except that my tach only works when im in neutral and the same goes for my gas gauge and temp gauge the gas and temp go all the way up and the tach goes all the way down and it's really annoying and i cant figure it out so any help would be extremely appreciated it's my dream car or it will be when i get my gauges working lol
thx in advance