And they even had a 402 BBC with a two bbl carb. I had one in a 70 impala 2 dr..
In 1970 John DeLorian started to consolidate the vast inventory GM was carrying for all the different vehicles. Thus many of the engines that were close to each other in bore size were more or less forced to use the 4 1/8" bore. That eliminated a lot of excess inventory and cost. The SS 396 was a trade name and good seller so it was kept.
The change caused a lot of confusion at the part stores back in the day. As there was a 400 SBC that used the same rings but different everything else.
Problem with the 396-402 BBC engines is they have been abandoned on the performance scene.
Most all BBC performance parts are based on the 4.250+ bore blocks and even basic engine parts like pistons, rings, heads and correct bore gaskets are harder to find.
I have had several fresh 396-409 cube blocks for sale for years. Only thing that makes them worth anything to a buyer is the build dates.