According to the Motor Emissions Application Guide, Chevy did not manufacture a 1976 pickup with a 427ci engine. You may be able to get it certified in California after visiting a smog check referee center however the process may be tedious.
Here are some guidelines the California Air Resources Board has put in place concerning engine changes:
A federal Environmental Protection Agency (EPA) certified (federal or 49-state emission legal) engine cannot be used in a vehicle that was originally certified for California. This obviously only applies if the truck your thinking of buying was originally California emissions certified.
Secondly, you must ensure the engine and emission control configuration are certified to the year of the truck or newer. You must not mix engine and vehicle classifications which will degrade the emissions certification standards. For example, a heavy-duty engine cannot be installed in a light-duty exhaust-controlled chassis even if they have the same displacement.
Also, if a computer-controlled engine is installed in a non-computerized vehicle, the "Check Engine Light" or "Malfunction Indicator Lamp", the diagnostic link, all sensors, switches, and wiring harnesses from the donor engine must be fully installed and functional. You may not mix and match emission control system components.
