A 400 will have a very large harmonic balancer, with a weight cast into one area- - - -those engines need to be externally balanced. Ditto for a flywheel or an automatic trans flex plate- - - -there's a balance weight on it if it's on a 400. The "T" prefix on the engine number generally means it's s truck engine- - - -probably with 4 bolt bearing caps on the number 2,3, and 4 main bearing webs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!