I believe it should be a screw-in filter that screws in the front left of the carb. I say believe it to be because in 1968 it may be a canister bowl type near the fuel pump if it had vacuum wipers. But I'm not 100% sure about that. I've forwarded your question to some others to clarify. It's not quite as easy of a question to answer as it first appears because of the variations of models, years and running changes.
(edit) Attached is a picture of a 100% original setup from a very early 1969 AMX. The car is a '69 but, as many early cars did, it had some '68 items on it.
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Last edited by Big Bad AMX; 01-26-2007 at 02:21 PM.