My understading on the 400/402 deal is that the "real" 400 is a smallblock (I have 3 of them) and that the bigblock 396 was "labeled" as a 400 in some applications when the 400 motor was defined as GM's largest powerplant.
The 402 came about as a machining error at the assembly plant necessitated the re-boring of many blocks to .030 over, thus creating a 402....but many of them were sold as wither 396 or 400s. What a mess.
One other use I've seen to differentiate is that SB seems to be used occasionally to represent StoveBolt, SBC for smallblock and BBC for big block.
Sorry, Caroline...if it was clear before, I'm afraid that I just muddied the waters.
