1970 Z28 Carburetor (780 cfm Holley) A/T List 4490 GM # 3972120
4 Spd List 4555 GM # 3972121
A/T w/NB2 List 4554 GM # 3972122
4 Spd w/NB2 List 4489 GM # 3972123
This is from
www.nastyz28.com
I spent a lot of time trying to figure all this out about the CA emissions. The 4489 has a different front bowl than the 4455.