I have a 69 Coronet with a stock 318, the carburetor is leaking I was wanting to swap to a four-barrell without changing my Intake Manifold is there any suggestions on how, and what kind of Carb do I need.  

I just recently swapped out my two barrel intake and carb on my 84 d 100 with a 318 ,I replaced the stock thermo quad with a carter racing carb ,it has small primary and secondary butterflies,works great on my stock 318 great power and excellent fuel milage as my fuel milage increased about 4 miles to a gallon using the carter 4 bbl as to the stock holley 2 bbl  

Ah, so it's a done deal. Glad you are running good.