Morning Greenfielder,
1974 is about right, I guess. Depending when in '74 it was built and assuming up to 12 months for delivery and storage etc., it puts the machine as a '75 build (?) which seems about right for that style?
It's been my experience that parts mules are hard to come by WRT HD8's in that most of the machines I see for sale are still too good condition wise to be parted out

Is there anything in particular that your chasing?