Hi Ralph,
I am not that familiar with the rules to define the PAD size but you might be able to retrieve information from the LCDK kit that uses the TMS320C6748BZWTD4E.
Some PCB and GERBER files are provided. You might be able to open it with some tools to check the PAD size:
http://processors.wiki.ti.com/index.php/L138/C6748_Development_Kit_%28LCDK%29#Hardware
Also the the board information of the Spectrum Digital AM1810 board are available:
http://support.spectrumdigital.com/boards/evmam1810/revc/
Since AM18x/OMAP-L138/C6748 are comparable in term of ZWT package this might help.
Anthony