Most Mk2 to mk2 or Mk2b to mk2b dash's are interchangeable
however upon fitting, the car and dash WONT talk properly
The mileage clock will flash
You may get random errors - even though there is nothing wrong
But before condoning the cluster
Have you had a live data read out - to see what the car thinks the vehicle is doing?
If the cars thinks its doing only 10mph, the dash will display 10mph
To me that would say there is a duff ABS sensor component somewhere
If the car says yes im doing 32mph and you've got 10mph = i would sway more towards dash
If the dash is at fault - proxy Alignment is requires
A decent Auto Electrician - fiat Stealer (very expensive) can do this task
OR
You can buy and pay for
MES (Multi ecu scan), its a cracking piece of software, and will allow you todo Fiat/Alfa/Lancia Diagnostics yourself
and carry out procedures like the Proxy Alignment
Where it makes all the components of the car talk correctly to each other
Another Note
ENSURE THE NEW DASH HAS LOWER or Near Spot on mileage to yours
A HIGHER DASH CAN NOT GO BACKWARDS, ONLY FORWARDS
So if you have 88K, a 99K Dash is useless (10k mileage added = less value)
Vs a 60K Dash been fitted, corrected to 88K = Everybodys happy
Ziggy