The 1967 Q-Jets are scarcer than others for several reasons, most already mentioned in this thread:
(A) Pontiac usage on GTO, Firebird, and 428 large car only, all other Pontiac V-8's used Carters
(B) Only year of "non-smog" Pontiac Q-Jet, many were transferred to other years (1968, 1969, etc.)
(C) O. E. applications were identified by tag only, many cannot identify these units once the tag has been removed.
(D) Commercial rebuilders converted to better selling bowtie
applications with use of elbow adapter.
(E) Quote HRM "get that quadrajunk off your engine and replace with a Holley". Lots of people actually believed HRM (and went slower!). Holley was a big advertiser with HRM!
While the 1967 unit is not the unit to build for 600 HP engines, properly restored, they are pretty much trouble-free, and work extremely well for stock or mildly modified engines.
Tremendous demand for these carbs, we have more requests for the 1967 than any other year. Low supply, large demand (seems I remember something along those lines from marketing class long ago).
Jon.
__________________
"Good carburetion is fuelish hot air".
"The most expensive carburetor is the wrong one given to you by your neighbor".
If you truly believe that "one size fits all" try walking a mile in your spouse's shoes!
Owner of The Carburetor Shop, LLC (of Missouri).
Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings.