Hi Daniel,
Saw your car down at the mechanic the other day while my nissan patrol was getting a service.Hope you were happy with him.
As for the fuel gauge it gets 12volts straight off volt regulator which is mounted behind speedo.get a test lamp and see if you have 12 volts at wire on sender unit.If there is 12 volts remove sender unit and check the resistive wire on the arm(ensure fuel tank is nearly empty before removing sender.)
as for speedo theres an instrument man (st george instuments) on th Grande parade at Sans Souci just near the shops at ramsgate rd .
Regards Felix

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1966 mustang coupe 289 auto
1970 mgb roadster auto
1970 cooper S mk2
1976 mini S
1964 wolseley 24/80
http://s160.photobucket.com/albums/t173/1966mini/