Hello;
The best way to find a replacement for that board is through its main features, such as sample rate, input resolution, number of analog input, etc.
After you gather that information for the board you currently have (its Users Manual), you can cross check those specs on page 183 of the 2003 catalog. There is a table on that page where you can find the board that is the closer fit for your old hardware.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments