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I think I read somewhere that the very early road test SD cars were ringers with a different cam.
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The original road test cars were not ringers, they were pre-production models that used the RAIV cam. This was the intended setup for the SD-455. The SD-455 story is fascinating, and a tribute to how grit and determination by a few engineers allowed these cars to be built.
The pre-production SD-455 Trans Am's were built with the RAIV cam, and they passed the EPA emissions test. But the EPA discovered that Pontiac engineers rigged the EGR valve to close after approximately 50 seconds, which just happened to be a few seconds after the standard EPA emissions test was complete. The government was not amused, and they failed to certify the SD-455 for production. Pontiac then had to go back and re-do the setup, elminating the RAIV cam, assigning a new casting number to the intake manifold, and get the whole thing re-certified by the EPA. This is what caused the SD-455 introduction to be delayed, so these cars did not appear until very late in the 1973 model year. Also, because the certification process was so lengthy, and anything from a simple air cleaner change to hood change had to be re-certified, Pontiac decided to build the Formula SD-455 cars with the Trans Am hood, which had already passed the EPA tests (that's the reason the Formula SD-455 cars did not come with the Formula twin-scooped fiberglass hoods).
But in the meantime, the pre-production SD-455 Trans Am's made the rounds in auto magazines, and ripped off mid-high 13 second blasts completely stock (with the exception of an open hood scoop). Amazing performance for an engine with 8 to 1 compression, in a car weighing 3800 lbs, with a steel intake manifold, 3.42 gears, restrictive exhaust, an auto trans, and stock tires.
But when Pontiac had to remove the RAIV cam and put in their boiler plate special .408 lift cam, the cars slowed to around 14 seconds flat in the 1/4 mile. Still amazing performance considering all the other handicaps mentioned above. No cars were delivered with the RAIV cam. The SD-455 engines were quite special, and they weren't simply parts thrown onto a standard 455 engine. The SD-455 used a special block, connecting rods, distributor, carb, intake, heads, and camshaft.
