Thee is an oversized bell housing, flywheel, and clutch assembly that's used on some of the big block gas V8's in dump trucks, but I think they're set up for heavy duty Clark or Spicer 5 speeds. I don't recall ever seeing the big input shaft being used on a 420.
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!