Carb too big?

Hey gents,

I am working on my new to me 74 duster with the slant 6. I have had it about a week now. I am working on the carb and it has a 750 CFM edelbrock manual choke 1407 model. currently the vehicle is not running, but I did have progress. I had a really large back fire out of the carb. any help would be awesome.

I am not sure if it is the distributor that is causing the backfire, but really learning as i go.