the fuel guage jumping down and say empty when you still have a half tank or so left left is quite common,
it is caused by the dry solder on the back of the board or the circet braking and not conecting.
needs to be taken appart and resolderend or bridged with a bit of cable,
there is a good write up on calaisturbo, ill find the link for you.
as for the clock could be shorting or a fault in the indercator stalk, electrical fualts are hard to figgerout with out looking at it personally.
there is two ways posted in that thread, it could bejelpful to you
http://calaisturbo.com.au/showthread...ght=fuel+gauge