Scott - I dont recall the exact differences but I recall not finding one in the list that was close enough. At first this was a giant experiment, and I didn't want to mess with the stock hardware configuration so I could easily switch back to Mach3 if I failed. So I really wanted the bitfile to match my hardware, and did not want to have to start rewiring stuff.
I think the bitfile is posted in the wiki. If not let me know. But if you need custom stuff, just message PCW_Mesa - he's the "mesa" guy aka Peter Wallace. He can adjust the bitfile however you like. I did try to program it myself w/ xilinx software but was horribly overwhelmed.