Speedo repairs

The speedo in my car need a rebuild. It's doing that thing where it waves at you, tells you the speed you are doing is somewhere between 40 and 50Mph.
Where can I get it rebuilt or even replaced?
Also the fuel sensor in the tank is out of a vl Holden. Since a VL has a very wide and flat fuel tank and the MK1 has a very small and tall tank I get some great readings. It sits on full and then rushes to half, has a small rest and then drops to empty. Once it reads half full I need to find a service station fast or it's going to be a long walk.
I live in Brisbane.
Where can I get it rebuilt or even replaced?
Also the fuel sensor in the tank is out of a vl Holden. Since a VL has a very wide and flat fuel tank and the MK1 has a very small and tall tank I get some great readings. It sits on full and then rushes to half, has a small rest and then drops to empty. Once it reads half full I need to find a service station fast or it's going to be a long walk.
I live in Brisbane.