Text below from this page re Test car # 9723 w/ pics, note 400 etc different than sheet shown.
http://musclecarfilms.com/1969_Fireb..._Cars_4_A.html
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~ Pete
"...The Pontiac Engineering Group built this mule car to test the feasibility of high performance 1969 Firebird 455.
They started out with a lightly optioned Carousel Red 1969 Firebird 400 (marked Test Car #9723). Using one of their new Pontiac 455 blocks, the engineers topped it off with a
set of Ram Air IV cylinder heads, Ram Air IV exhaust manifolds, and adding to the "wow" factor, the engineers went to the parts bin and brought
out a 3-year old (1966) Tri-Power setup. Underneath the Firebird was a very unique Vacuum Operated Exhaust system (known as VOE)
consisting of vacuum-operated bypass valves mounted on the mufflers. The driver could choose an "open" or "closed" exhaust note using a pull
knob mounted under the dash (this setup would actually become a short-lived and very rare production option on the 1970 GTO). Finally,
funneling the exhaust gases out the back of this special 1969 Firebird was an exotic looking Ferrari-style 4-tailpipe setup. The transmission was the
ever reliable Turbo 400 with a modified valve body to provide firmer shifts. A 1969 Trans Am rear wing was added to the rear deck lid, and to
make the car stand out visually, black accents were added all around, including sword-shaped stripes on the hood scoop nacelles, black stripes on
the body "wind splits", blacked out headlight bezels, blacked out tail panel and rear valence, and blacked out grilles. A set of "455" emblems
(pirated off a 1970 Bonneville) graced the hood scoops and trunk lid. Riding on the factory Rally II wheels with Goodyear F70-14 bias-ply tires,
Test Car #9723 must have been a real handful to control. As wild as this setup was, the 3-year old Tri-Power setup and the 4-tailpipe exhaust
system were obviously not intended to be production items. Before Pontiac Engineering was through with this car (late 1970) they attached a large
front chin spoiler, which seemed to resemble the spoiler used later on production 1970 Chevrolet Z/28's.
An interesting note here is that the engineers dubbed this engine a "455 H.O." rather than a "Ram Air IV 455", even though it contained Ram Air
IV heads and Ram Air IV exhaust manifolds. Naming this engine in the famed "H.O." (high output) series rather than the "Ram Air" series may
have been simply because the car did not use a Ram Air setup. But technically, this was a Firebird Ram Air IV 455, with the exception of a 1966
tri-power unit..."