You gotta love peoples "car knowledge"

From a "Big Block Chevy" casting number book: http://www.ajgeneral.com/bbc_block_casting_numbers/

Appearing in 1966,to the approval of Chevy fans and the detriment of the competition was the 427.Reaching it's zenith in 69 as an exotic all aluminum block and heads high performance engine known as the ZL-1.A hand full of Corvettes and Camaros received this option and that makes then extremely difficult to find today.Most ended up as drag racing engines and so not many survived.

Mark IV engine have also been converted to truck blocks,or "tall blocks".Although essentially the same as other big block Chevys,they feature a longer crankshaft centerline to deck distance and are not normally considered desirable for passenger cars.The only was to know is to check the cast numbers.

1969 was officially the last year of the 396 but,many cars were know as 396 SS's afterward.A slightly larger bore gave the 396 a displacement of 402 CID for the 1970 model year.Many of these vehicles were marketed with 396 SS emblems on the fenders and 402 on the sticker under the hood.To make things more interesting Chevrolet marketed some of the 402 as Big Block 400 engines,like in 71.So if you have one of these engines,it's a 402 or a slightly bored out 396,you get the point.As a result Chevrolet described the big block as a 400 4 barrel and the small block as a 400 2 barrel.