84z28Camaro

So in my 84 z28, I've had a persistent electical issue where the volt gauge would shoot way up to its max and stay there for long periods of time. The alternator was replaced about a year ago and it didn't really fix it. The car does have an amp and 2 subs in it, could that be messing something up? There is also a short somewhere for when you turn the headlights on the tach gets stuck where it is and the oil gauge bottoms out. Could the short be causing an issue with the rest of the system?