360 magnum

Do yourself a favor and read this site:

http://www.magnumswap.com/required-modifications/

http://www.magnumswap.com/automatic-transmission-details/

"The 5.9 Magnum uses a weighted flexplate and a neutral-balanced converter from the factory. To make life simple, be sure to get the flexplate with your engine. With the weighted flexplate, simply use a neutral balanced converter, these are readily available for most transmissions. We recommend this method."

LXguy has done alot of coverage on it.