hello,
The 402 is semi rare,
it actually is an overbored "396".
the plant the "396" was assembled had a little trouble with the alignment of the boreing bar, so legend goes.
mid year 1969 and up, all "396's" are supposedly 402 cubic inches by the increased bore size needed to fix the problem. In some cases such as trucks and large cars they are referred to as "400's".
hope this sheds some light on the subject.
BRANT