Look at this link on team chevelle I replied too.
http://www.chevelles.com/forums/showthread.php?t=217258
For my 68 L78 nova I had a hard time finding the correct motor mounts for my original frame mounts. A friend at gm came up with this part number GM# 6258154 and they fit perfect(And still avaliable). I think they are the same for the small blocks?
Jason