I have not worked with FullCalc, however, I do transfer files back and forth between AppleWorks and Excel a lot.
From FullCalc, if you are able to SAVE AS "ASCII TEXT", you should be okay. Once saved as ASCII text, open the file in Excel. You will be taken through a series of menus. Choose "Delimited" in the first window; "TAB" in the second; and click the "General" radio button in the third.
You will then have all of the "data" (but not the equations, unfortunately) from the FullCalc. Also, you will lose whatever formatting you had in FullCalc i.e. decimal precision, alignment, borders, etc.
... but it beats having to transcribe all the data by hand.