EXCLUSIVE: Three-time Oscar nominee and original John Rambo actor, Sylvester Stallone, has come aboard Lionsgate, Millenium Media and AGBO prequel John Rambo as an executive producer.

Sylvester Stallone is returning to his iconic Rambo franchise in a brand-new role for the anticipated upcoming prequel movie John Rambo.

Bo Gritz, a Vietnam War hero who inspired Sylvester Stallone's character John Rambo in "First Blood," is dead. Bo died Friday at his home in Sandy Valley, Nevada ... according to his wife. His official cause of death is unclear, but Bo's wife…