You gotta love peoples "car knowledge"

Chevy bored the 396 out to 402 inches in 1969 or 1970, I forget which. They still called them a 396 in sales brochures, fender emblems, air cleaner decals etc, because the 396 had become a very popular engine and they didn't want to turn off any potential new buyers.

In '71+ when companies were starting to build "insurance beaters" they made the 402 available in the Malibu and the Chevelle with the Heavy Chevy option. These had "400" fender emblems, were listed as a 400 in sales brochures, and the sticker for tune up and emissions information in the engine bay even listed it as "400 cubic inches".

I know all this because a good friend in high school got his dad's Chevelle which was bought new in '71 and never modified. It was a standard Malibu, green/green, flat hood, "400" fender emblems, bench seat, column shift th400, and 402 big block. We cruised quite a bit in this car and it did ok for being low compression and totally stock.

PS-
Just found this website - evidently there's one devoted to the Malibu 400:

http://www.shapeconsulting.com/malibu400/400facts.htm