I was just looking through my Delco Rochester Carburetor Parts and Service Manual.

Were there really 10 different Quadrajet carburetors for the 70 Chevelle big block?

http://www.chevelles.com/showroom/temp_10carbs.jpg

complete page here (http://macc.chevelles.net/70carb.htm)

I am showing the same thing in my casting number book for the big block 70's. 704200 was on the 396/400/454, 201 on the same engines, 204, same engines, 205 same engines, 221, same engines. I am guessing there were this many for the various HP outputs and the differences for a manual tranny.