found this -
Engine Family LxWxH in inches, without carburetor. Weight in Lbs.
221-260-289-302 29 x 24 x 27.5 460
Boss 302 29 x 24.5 x 28.5 500
335 Series 351 Cleveland 29 x 25.5 x 27.5 550
351 Windsor 29 x 25 x 29 525
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and this from another forum -
#7 • Dec 14, 2008
I come up with 22.5" for the C, and 19.5" for the W, measured from the top of the exhaust port face.
With stock passenger car manifolds, 24" for the C, 23.5" for the W.
Something to keep in mind for header clearance design, is the W has a vertical exhaust face, the C is aiming 45° down. The W will need a larger radius for the downturn, in the C the downturn is part of the head. The Cleveland starts out wider, but with exhaust in place they end up about the same