Help with 73 Duster stalls when put in gear

Hi, I finally got my 73 Duster running after 2 years and several parts later. It would run and then miss bad. Finally narrowed it down and purchased new TSP distributor and coil. Now it runs, just need to mess with timing a bit yet but when I put in reverse, it stalls. Not sure if it could be the carburetor (since that is about the only thing that isn't new) or if I should be checking other things first. Any help here would be appreciated. Thanks.