There is an FD with a blown motor for sale in the sales area:
http://www.rx7forums.com/forum/viewtopic.php?t=414
Good luck.

Sure he can build a 500 HP 13b but he wont have the reliability of a LS1/T56 FD. The LS1 has amazing gas mileage for it's HP as well. The 6th gear really helps. Go do a search for Hinson Supercars for LS1RX7 engine mounting kit. You will need to give them your stock sub frame as a core and wait about 3-4 months. Don't go with the Granny's kit. I heard they suck major.

Justin