If you run them on a stockish Long Ram car you'll want 1405/1406's (06 is electric choke, 05 is manual). These are 600 cfm carbs and will match up well with your setup cfm wise, I'd reccomend the 1406 for ease of drivability. You should also get a jet kit for them because they'll likely be a little rich for that engine as they come out of the box since stock 2903's flowed in the 500's.

You will find that these are not a direct bolt on replacement to the stock 2903's either, you will have to use different air cleaner bases, make some custom carb linkage adaptions, and likely fuel lines as well.