77xcgs

hi,can anyone help me?ive got a 302 that seems to syphon back fuel if the car sits for a week.if i start the car,its fine for about 3 or 4 days,and will start first time.from weekend to weekend it becomes a mission to start,ive replaced plugs, leads,fuel pump,done the timing,taken the car to a carb specialist who checked and tuned the carter thermo carb and he also told me there was a problem with fords of tha era having fuel leaking back when the 302 sits too long.the car is a one owner with genuine 59000kms,so i really want to keep it in good condition.any advice will be much appreciated.apart from this problem the car runs perfect,please help!