Speedo and rev counter jumping

Need your advise.
Car was standing for a year. Opened the engine for H-conrods and changed ignition for
wasted spark.
As there are a few problems which I will be able to solve, there Is a major problem with the speedo as it is jumping or most of the time fixed at 80km/h when the car is standing and running. The rev counter is jumping around permanent.
Any idea what could be the problem?

I pulled the wasted spark cables below the driver side dashboard, but took care and I don?t think that I hurt some of the other cables...

Sounds like a bad ground on the cluster? Car standing outside, leaked water?

Fixed at 80 km/h is very odd.

And no power taken from somewhere where it can cause interference? Not sure if possible with this coil-powerstage combination.