ok good. The pre-86 700's were prone (i'm not sure prone is a good word..inevitable maybe?) to detonating when put between a high torque motor and a heavy load. The 400 is actually longer than the 700 i believe.
http://72.14.209.104/search?q=cache:...s&ct=clnk&cd=3
http://www.smokemup.com/tech/700r4.php
couldn't find much else, the TH350-700R is a more common conversion.