I cover how to build one for an A833 4 speed in these posts:

http://www.clubhotrod.com/forums/showthread.php?t=14794

http://www.clubhotrod.com/forums/showthread.php?t=15090


Basically, you need an early Poly or Hemi Flywheel, and the correct spacer plate for parts along with the correct bellhousing. If the flywheel is not drilled it will need to be. Takes a little work, but is usually a lot cheaper than the $700-800
For some on the market.