This happens to me on my 74 whenever it is cold, I have a manual choke, at first I have to pull it about 3/4 out on a cold morning, but as soon as it starts I have to go to about 1/4 choke, if not it dies every time. I have tried and tried to see if I could adjust or play with the carb. but no matter what, that is how mine works, and I have headers also.