I have a 65 mustang that sat for about 4 years that I bought a few months ago. I did an oil change and put new brake pads on it and drove it from oregon to arizona with no problems. I drove it a couple weeks at home and decided to rebuild the carburetor. The exhaust was leaving carbon on the ground when starting and is still doing so. Now it is sluggish when starting from stop and occasionally just dies. When I restart it, it runs fine until you put it in drive then it dies again. If I wait about 10 minutes, she starts right up and runs fine. I have been told that she is running too rich. Does that sound right? She is also going throught ALOT of gas. I dont have a working gas gauge, but she is getting less than 10 miles a gallon with an I6. I am currently having a 289 rebuilt to put in her, but Im not driving her since shes unpredictable. I would love to figure this out since Id rather drive her than any other car we have, im sure you understand. I am a novice with engine work, but trying to learn. Please ask any questions that I havent answered, Ill be checking back alot. Thanks in advance.

65 Coupe
Original I6 Engine
C4 transmission