[THI]

I wish I had the original air cleaner to my 1979 C3500 but it was long gone and replaced with an open element by the time I purchased. My 1978 C20 has the original air cleaner, but the 1978 came with a whole lot less pollution equipment - no canister, no EFE - basically a PCV, hot air to the air cleaner and spark control (Spark TVS). According to the GM reference above, CA and Fed came with the same equipment for HD emissions (over 8,500 GVW in 1979 so the picture for the diagram above would be correct.