My quadrajet leaks down over night making it hard to start cold ,however after that its ok the rest of the day.It also whistles at 55mph and gets about 8 miles per gallon. I thought it could have a vacuum leak , but I put a vac gauge on it and pulls 12hg at idle. I don't want to rebuild this carb because it might have worn throttle shaft or other internal leaks common quadrajets .What would be a good replacement and would I need adaptors. Any help would be great. Also its a 350 cu with 4.56 gears ,th400 trans Thank you from Kansas.