Dear Sir/ Ma'm, with a high score such as 642, you can expect an All India Rank of 1-472 if you are a general candidatewhereas this rank will go down if you are a reserved category student. According to previous year' cut-offs, the Sawai Man Singh Medical College, Jaipur had a cut-off of 610 for general category students in the 85% state quota counselling. If you belong to any reserved category then the cut-off was much lower. SO you have a pretty good amount of chance.