Has to be Paul Westhead (1963-1964).
He's only 78 and out of coaching. Bring back his 130pt per night offense (but not the no-defense part).
Side note, but his wikipedia coaching resume is amazing. He is the only coach to win title in both NBA and WNBA. He's been head coach of NCAA Men, NCAA Women, NBA, NBDL, WNBA, and 2001-2003 he was head coach of the Panasonic Super Kangaroos of the Japanese Basketball League.