@DionR I don’t know who told you that load of crap about the 340 being an upgrade. Weather you see it or not as so, the way it was done was strictly by the engines CID.
Maybe I didn't state it correctly. Wasn't trying to say the factory saw the 340 as the better motor, only that I thought the 383 was the base engine for some E-Body model and that for a small price you could "upgrade" to a 340 4BBL. Can't figure out what model it would have been (not a T/A or AAR), so I must be wrong. Had it pointed out to me in a thread on a different forum and it seemed like I remember seeing that before, but didn't verify it then and couldn't just now either.