I assume that by "x format" you mean going from .mod to .xmod files.
Under the Options menu go to the "Export and Clipboard..." item. On the Clipboard tab you'll see two options for the text format. Select the "Fixed-length text (V7)" option. OK the dialog and save the model.
Now you can copy long strings of numbers to Excel and they'll come across identically instead of having Excel convert them to scientific notation.
It seems to me that the new tab delimited clipboard format was introduced with v8.