From things I have read, many (if not all) of the '69 TA's used for racing were merely Camaros converted with a Pontiac bumper and hood.

There was indeed an awesome Pontiac 303 in developement but it was stopped.

From wikipedia,
"303 - The revised engine had shorter connecting rods, smaller 2.5 in. (63.5 mm) journals, special "tunnel port" heads, and a solid-lifter version of the 400's Ram Air IV camshaft. It shared the 4.125 in (104.8 mm) bore of the 400, but with a 2.84 in (72.1 mm) stroke for a displacement of 303 in³ (5.0 L). The short-deck engine weighed about 40 lb (18 kg) less than the 400, and had an 8000 rpm redline. The 303 program was promising, with race-ready engines producing 475-525 hp (354.4-391.7 kW) and slated for advertised ratings of 355 hp (265 kW) in the Pontiac Firebird and 375 hp (280 kW) for the Pontiac GTO. Concerns about emissions, the response of the automobile safety lobby, and the warranty implications of a high-revving street engine led to its cancellation. SCCA Trans-Am series General Competition Rules required an engine to be a "Production" item, and required a production of no less than 250 units. The total number of Ram Air V 303 engines produced is not known, estimates range from the SCCA required 250 units, up to 500 units, with rumors of a handful of Ram Air V 303's making their way into the Pontiac Trans-Am production line. These engines are extremely rare and parts not readily available."

As in many other instances, Pontiac got hind tit with Chevrolet getting all the support needed even though Pontiac probably had the better stuff.